Sewing method, Topstitching with fleece.
I do the construction seams with fleece, with a stretch stitch, fleece has a bit of stretch.
Then finger press open the seams, and apply a strip of wondertape or wash away tape directly on the seam on the wrong side of the garment. Place some bias tape or I use foldover elastic on top of the tape.
Flip to right side and topstitch on either side of the seam, the effect is 3 rows.