I've only made one - my Dear Jane. My scallops were as many as the triangles on the edge, but I made them deeper than the original, and I used a narrow bias edge.
I did make it double, to make it easier to stitch down on the back, and I tucked a crease at the junction of each scallop, which I stitched down, just as I would the mitre on the corners of ordinary quilts.