I do not trim away the batting or the backing fabric until after I sew the binding to the front of the quilt. Then I trim away the batting and backing but I leave about 1/8 of an inch beyond the edge of the fabric. I also cut my binding 2 1/4 inches wide instead of 2 1/2 inches. I fold the binding over and hand stitch it to the back. I entered my first quilt in a show and the judges critique was that the binding was not full. I learned how to make full binding after that.