When sewing a blouse or a jacket, the most difficult time is when you need to assemble and attach the collar. You might invoke the Gods of sewing but it seems they have become deaf because you cannot skip this step. Every tiny error will be highly visible, so to avoid the pressure, you can already get prepared for a breathing exercise generally advised before birth giving.
Before you start assembling your collar (shirt collar, reverse collar, Peter Pan collar, stand-up collar or soft collar) you should read this:
The collar should fit perfectly in the garment neckline. If during the fitting you change the neckline, you must change the collar accordingly. And especially to carefully report all the notches (mid back, shoulder) on the collar and the neckline.
In order to have an impeccable collar, the upper collar is a little longer than the under collar. This will prevent corners getting up once the collar is attached. This extra length varies from one type of collar to another (folded or flat collar) and the thickness of the fabric.
Generally, the collar is sewn and attached after the shoulder seams and before the side seams.
So far, nothing is very complicated really. And now let’s get to work:
Interline the wrong side of the collar, either the upper collar or both the collar sides. The fusible interlining should have the same shape and size as your collar. But before ironing the interlining, erase all your felt pen marks from the collar fabric and replace them once the collar is cooled.
Pin the two layers of the collar, the right side against the right side, matching the seam lines
Curve the under collar to get the extra length. Pin the layers together along the outer edge and stop at 5 cm from each corner. Bend the ends of the collar and finish to pin the edges together.
Sew along the outer edges of the collar. Trim seam and corner allowances. Figure 5. For some collars (the reverse collar), stop sewing just above the assembly line. Figure 5a
Turn the collar on the right side and get out the corners not pushing from the inside but gently pulling out with a pin.
Baste stitch the edges of the finished collar. Iron. Curve the under collar and bast stitch slantwise
Your collar is now ready for sewing and you can breathe normally.
The steps outlined above are taken from the book “Burda: a practical sewing guide” that I found complete and with nice drawings. But not as pretty as your finished collar, isn’t it?