I have also written a blog post on interfacing, you can read it here:
Janzi Coat : Interfacing and Notions
Below are some photo examples from my sample. I have used a beautiful wool coating fabric from Potter & Co for this.
Side Front
Step 4: Place one of the side back panels against the centre back panel, right sides together. Align the edges and match up the notches.
Sew along this edge using a 1cm (3/8in) seam allowance.
Press the seam open. Repeat for the other side back panel.
Step 5: Take one pair of your centre front/centre front facing pieces. The pattern piece you printed for these parts were the same to save on space with printing.But we will be trimming down the lapel of one pair to make it the centre front.
Take 1cm (3/8in) from the side of the lapel, tapering into nothing at the waist notch. And take 0.6cm (1/4in) from the top of the lapel, tapering into nothing at the notch.
The untrimmed pair will be the centre front facing pieces.
Step 6: Optional step
Flip the centre front pieces over to the wrong side / interfaced side.
Mark on your roll line in chalk.
The roll line is where the coat lapel folds over. We want this to maintain its shape and not stretch out over time, so we will be hand sewing cotton twill tape in place. The roll line of this pattern starts 1cm (3/8in) down and out from the neckline and ends 1cm (3/8in) in from the notch at the bottom of the lapel.
Run a hot iron with steam over your cotton twill to pre-shrink it. Measure your roll line and cut two pieces of cotton twill, 1cm (3/8in) shorter than this measurement.
Pin the cotton twill in place, just inside of the chalked roll line. Distribute the ease of the lapel evenly throughout.
Catch stitch the cotton twill tape onto the centre front, making sure the stitching is mainly catching the interfacing, and only tiny sections of fabric.
Step 7: Place one of the side front panels against the corresponding centre front piece, right sides together. Align the edges and match up the notches.
Sew along this edge using a 1cm (3/8in) seam allowance - making sure you flip the pocket bag out of the way so it doesn’t get caught in the seam.
Press the seam open.
Repeat for the other side front / centre front pieces.
Step 8: Place the front panels against the back panels, right sides together.
Line up the front and back shoulder seams, ensuring the seamlines match.
Sew along the shoulders, using a 1cm (3/8in) seam allowance.
Press the seam open.
Step 9: Place the front panels against the back panels, right sides facing, so the side seams are aligned. Match up the notches.
Sew down the side seam using a 1cm (3/8in) seam allowance, making sure to flip the pocket bag out of the way so it doesn’t get caught in the seam.
Press the seam open.
Step 10: Take the top sleeve and under sleeve pieces in the main fabric. Fold the hems up at the notches, wrong sides together. The interfacing should help guide where to fold to.
Press well with steam and let the folds set.
Unfold the hems. Place one of the under sleeves against its corresponding top sleeve, right sides facing together.
Match up the curved edges with the double notch. Sew along this edge using a 1cm (3/8in) seam allowance.
Press the seam open. Repeat on the other sleeve.
Match up the remaining edges, with the single notch.
Sew along this edge using a 1cm (3/8in) seam allowance. Press the seam open.
Repeat on the other sleeve.
Step 11: Set your sewing machine to a longer stitch length and sew a basting stitch around the sleeve cap (the top half of your sleeve).
Make sure this basting stitch is just within the 1cm (3/8in) seam allowance, and you leave tails of thread at each end.
Gently pull on the bobbin thread to bring in the fullness of the sleeve cap.
Turn the body of the coat inside out. Turn the sleeves out to the right side. Make sure you’re matching the right sleeve to the right side of the coat. You can tell which side of the sleeve is the back, because it curves out slightly to accomodate the elbow. It is the seam with the double notches at the elbow.
Place the sleeves in their corresponding armholes. Match up the underarm notch and shoulder notch to the underarm and shoulder seams. Match up the seamline at the sleeve front to the notch on the front armhole. Match up the seamline at the sleeve back to the notch on the back armhole.
Once these points are pinned in place, adjust the ease on the sleeve cap so it fits neatly within the armhole, making sure you don’t pull the basting threads too much that it creates gathers. Sew the sleeve in with a 1cm (3/8in) seam allowance.
Press the seam away from the body.
Step 12: Cut 2 lengths of sleeve head roll into shape. If you’re making your own, you can use the top sleeve pattern piece as a guide and follow the shape of the sleeve head, giving a little extra length for the back of the sleeve.
Or if you purchased sleeve head roll in a roll, you can cut it to the length of your sleeve cap and taper off the ends.
Push the sleeve back inside the body of the coat. Place the sleeve head roll against the sleeve cap and baste it to the seam allowance.
Step 13: Place the under collar pieces together, right sides facing. Sew them together along the centre edge, using a 1cm (3/8in) seam allowance.
Press the seam open.
Place the collar against the collar stand, right sides facing. They will be joined together along the dashed line, as shown. Bring these edges in to meet each other and sew along this edge using a 1cm (3/8in) seam allowance.
Clip into the curved seam allowance and press open.
Place the collar against the undercollar, right sides together. Match the notches, as shown.
Match up the corners and the centre back seam to the centre back notch.
The undercollar is slightly smaller than the collar, to allow the collar more room to fold over when worn. You will need to ease the collar into the undercollar when sewing them together.
Sew around the outside edges, using a 1cm (3/8in) seam allowance, leaving the bottom curved edge open for now.
Trim the corners off, and grade the seam allowance of the undercollar.
Turn the collar out to the right side and press it flat. The edges of the collar should be folding around slightly to the undercollar side.
Pull the remaining edge of the undercollar down to meet the edge of the collar, matching notches. Baste stitch together, 0.6cm (1/4in) from the edge.
Step 14: Place the undercollar against the right side of the coat. Match up the centre back notches along the neckline. Match the other notches as shown.
Sew the collar to the neckline, using a 0.8cm (5/16in) seam allowance.
Grade the seam allowance and clip into the curves of the seam allowance, if necessary.
This step may be tricky as you’re navigating different curves and bulky layers.
I find it helps to stop occasionally, with the needle down. While the needle is securing all the layers of fabric in place, you can lift your foot and re-adjust the fabric as needed.
Step 15: Optional step: Shoulder pads.
You may find that you don’t want or need shoulder pads if your fabric has enough structure.
Hand stitch your shoulder pads in place, to the wrong side of the coats shoulder seam. Tack the pads to the seam allowance, so the stitches can’t be seen from the right side.
Step 16: Place the centre front facing against the centre front of the coat, right sides facing together. Match up the edges and notches, keeping in mind that the centre front piece was trimmed down at the lapel in an earlier step. The facing will need to be slightly eased into this section.
Sew around the outer edge, using a 1cm (3/8in) seam allowance. Leave gaps at the beginning and ending of the stitching line, as shown.
Trim the corners of the lapel and hem. Grade the seam allowance.
Snip into the seam allowance at the waist notch. This is where the lapel begins.
Trim the extension off the bottom of the facing, as shown.
From the waist notch down to the hem, press this section of the seam allowance towards the facing. Understitch the seam allowance to the facing.
From the waist notch up to the lapel, press the seam allowance towards the main body of the coat. Understitch the seam allowance to the centre front.
Turn the facing out to the right side and give everything a good press. When pressing the lower half of the centre front seam, make sure the facing is pulled slightly in and can’t be seen from the right side of the coat. And when you press the lapels, it’s the facing piece that should be folding slightly over the seam edge.
Step 17: Fold the hem of the coat up at the notches, wrong sides together. The interfacing should help guide where to fold to.
Press well with steam and let the folds set.
If your fabric isn’t very pliable, you may like to run a basting stitch along the edge of the curved hem. Pull on this thread to slightly ease in the curve, making it easier to fold up in place.
That's it for the main body of the coat! Stay tuned for Part 2 of the sew along where we will assemble the lining and sew it to the main coat.