I started watching Nancy Zieman on public TV maybe about 20 years ago. In those days it was all about garment sewing. She was the only game in town and I consumed every word she uttered, taped every program, and bought every book. I truly have learned so much from her, much that has stuck with me for many years. Her approach is to use the simplest methods to get the most professional results. She is not into couture but more making it look like couture. Ever since I saw her do this collar I have been using it pretty much ever since.
My current project pattern, like most, has you put the collar together stitching the three sides not attached to the neckline first. Not Nancy! With her method you sew only across the long outer edge of the collar.
Grade this seam and press as sewn, then open, then to the undercollar side. You will then understitch the undercollar using a triple zigzag stitch. Make sure you set up your presser foot so that you don't stitch over the edge onto the upper collar. Give this another good press.
Love that stitch. This will prevent your undercollar from rolling out on the outer edge as well as give you a really flat edge. Once the long edge is all understitched, put right sides together again, matching the unsewn corners. This is where you will now check to make sure all edges are even and equal. Are they? If so, and that's rare, put right sides together and proceed to pin the short ends of the collar together. If not, like most collars I have sewn, a bit of the edge is off, it is time to fix it. Ever see collars that have uneven points when you look straight at the garment? Nasty. Fold your collar in half matching the long edges and corners. Trim the edges so they are equal. Your collar needs to be perfectly symmetrical. Double check front and back. If you are doing a tailored garment, like a wool coat, where you need to favor the undercollar, once the edges have been evened, cut the undercollar back a fat 1/16th of an inch across the neckline edge only. When you install the collar you will still match the edges but the undercollar will be pulled a hair tighter, preventing roll out. On a thin shirt fabric the zigzag understitching alone should take care of any undercollar issues. Once all even, pin the sides and stitch starting at the neck edge. A half inch from the point dial your stitch length down to 1.5. You don't want to secure the end with back stitching. Actually you don't ever want to do that. It makes lumpy, uneven seams. So always go to a shorter stitch length to finish off the seam. In the case of a collar where you will be trimming very closely this is doubly important.
Once the short seams are sewn, grade them, cut the fabric away at the points at an angle. Press as stitched then press open. I use the handle of a wooden spoon to press these seams open. Once pressed open, turn right side out, admire your sharp point and flat seam, and press again. Thank you, Nancy!....Bunny