Pink Perfection
There are 3 basic ways to scollop a quilt edge, that I know of. All 3 take planning, marking in advance.
1. The easiest, IMHO is to plan on an "envelope" or "birthed" quilt. Put down your batting then backing, then add your top, face down. Pin the edges very well. Mark, sew (except for enough space to turn it right side out) and clip. You will need to clip your curves and any sharp angles you decide to have. Sew up the opening by hand then baste and quilt.
2. The second happens after you quilt your piece. Mark and cut your scollops. Sew on BIAS binging, and finish normally.
3. The third, which I have seen on antique quilts is a sort of combination. You sandwich and quilt the whole thing, then add an edging, face down on the top. This edging should be at least 2-4" wider than your planned scollop. You then clip it, and turn the edge right side out and hem that strip to the backing.
On all 3, I think it is a good idea to go back and quilt along the scolloped edge.
If you want a different scollop or don't want to use a standard one, get a strip of paper the length of your fabric. (The person I saw used a wide adding machine tape). Fold it into as many pieces as you want scollops. Mark and cut this template, remembering to add seam allowance.