How to Sew a Bound Buttonhole
3. Open the buttonhole. On the wrong side, cut between the welt stitching lines and into the corners.
4. Turn the welts' cut edges to the wrong side through the cut opening. With the right side up, adjust the welts so they meet at the center along the buttonhole placement line; pin. Using small diagonal stitches, baste the welts together.
5. Fold the garment edge back. Stitch across the triangle. Trim the ends of the welts, and round the corners to reduce bulk. Then press the buttonhole face down on a soft surface. Finish the buttonhole. For a finishing technique, see the article "Bound for Beauty" in Threads #160.