I plan on joining my bias binding in the same manner I do on a straight binding quilt. It is the one where you open up the binding to lay it flat and sew the 45* angle, re-fold and continue stitching the binding. If you think about it, you are applying a bias straight edge to the scallops, so the same join should work. I am looking for a wide back for my scalloped quilt before quilting it this month.