I've always measured the sides of the quilt, cut freezer paper to this length, ( I fold & cut the freezer paper into 6" wide strips) then I fold the long strip - accordion style - over & over until I have the size scallop I want. Draw the curve, cut it out- unfold -- you have a row of scallops that fits the side of your quilt. You can iron the freezer paper onto the quilt to cut or mark your scalps. you need to figure out how you want your corners to round & finangle the lengths, corners.