Do you want all four sides to match?? I saw this on F&P. Decide how long you can make your "S" in you border so that the ends end up in a curve in your corners. Cut a piece of freezer paper the length of you border. Mark you curves on both ends. Then fan fold it, draw you "S". Trim and you will have perfect matched curves. HOPE this helps. Not sure which F&P show it was on. Never thought of doing it that way but it works.