Sewing it by machine is a two step process. Sew it to one side, usually the top, fold it over then hand stitch the back. Or stitch it to the back and use a decorative stitch on the front. I do it an even different way, sew it to the front, press three times: once to set the stitches, once to fold it straight over the edge and the third time to make the fold. Stitch in the ditch from the front where the binding meets the quilt. I just pin the corners but some folks use washable school glue.