Not sure I understand the question. You will need to use bias binding. I recently saw a youtube where Alex Anderson showed how she does scalloped binding. When she gets to the dip, she actually pulls the next scallop so the dip just about creates a straight line with the binding already sewn. She just keeps sewing straight to get across the dip and follows the curve of the next scallop. When she releases the scallop, the binding will fall into place.