Before you cut into the felt, suede, or ultrasuede trim away all the seam allowances surrounding the undercollar pattern piece
Cut out one whole undercollar on the fold
Pin this undercollar to the interfaced uppercollar, which has the seam allowances turned under (miter the corners of the upper collar), and catch-stitch the undercollar to the interfacing at the upper and side edges about 1/2″ inside the seam lines
Baste the lower edge of the undercollar to the neckline seam allowance, placing the cut edge of the under collar along the stitching line
Baste the undercollar to the uppercollar about 1/4″ (6mm) from all edges, then trim a scant 1/8″ (3mm) from all the raw edges
Using a small blanket stitch, sew the undercollar to the uppercollar and neckline seams. (See diagram below:)
