Several readers have asked about adding a collar to the Sewing Workshop's Peony vest. The last two times I have used this pattern, I have added a fairly simple collar.
The first one was the denim vest, which is a work-in-progress, but I wear it. Using Susan Brubaker Knapp's idea, I am filling it with seed stitch, leaving negative space in the shape of various creatures.
I walked my measuring tape around the neckline and added an inch or two. I then cut a straight-of-grain rectangle 6 inches wide X the measured length.
First I stay-stitched the neckline and clipped to the neckline across the back. Then I placed one long edge of the collar on the neckline and sewed right side to right side, 1/2 inch seam allowance. Then I folded the ends of the collar, right sides together, and sewed even with the center fronts of the vest, trimmed and turned. Lastly I turned the remaining raw edge of the collar under about 1/2 inch and slip-stitched in place.
The second one was the black wool-cashmere.
Again I measured the neckline, this time more carefully so that I could put in a seam at the shoulder line. There was no remnant large enough for the entire collar. I was able to cut the fronts along the selvage. This piece was cut 3 inches wide.
Again, I stay-stitched the neckline but I did not need to clip around the back with this fabric, and with single-layer construction, I wanted to avoid any clips. I chalked in a 3/8 inch overlap on the neckline. Then I layered the collar seam allowance over the neckline (wrong side of collar to right side of vest) and stitched down the middle of the layer.
For a little added stability, I stay-stitched around the raw edge of the black collar.
Another option would be to use one of the clever collars from the Sewing Workshop's Now and Zen pattern. One of those is an open-ended tube collar and the other is a double collar. Each has a clever finish that encloses the raw edges of the seam attaching collar to body.
So many options!