Donna Dewberry shows this technique on her new shows. She cuts the backing approx 4 inches wider all the way around the quilt top and batting. Then she folds the backing in half towards the top and presses the fold lines, and then folds a mitre on the corners pressing again, then folds it over again onto the quilt top, pinning it in place. Then top stitch it down on the sides of the quilt and where the fold lines are, but not up the folds of the mitred corners. It ends up with a pocket to put a rod through.