Valance looks very simple to do. Just measure the length and height you need add 5-6 inches for each tubular "jabot", then define how many scallops, size is individual chose, and draw on a paper a wave about 3-4 inches difference between highest in the middle and lowest point on sides. Then fold on both ends (concave part) jabots and you have pattern, adjust it if needed and transfer on the fabric, cut, add a trim and sew, add a sew on velcro tape loop side (not with glue or you'll break machine needle) on the top, and on the wall easy to attach stick on (with glue) tape, "hook" side.

frenchdecor, do you mean to attach the valance directly to the wall or would you recommend a rod or cornice that the valance would attach to?