This is theory, not practice but: take a square that is 2.5 inches or a little more, put a 2 inch circle (cut from cereal, etc box, must be stiff) inside it and mark circle. Do a running stitch around outside of mark, put circle back inside the drawn circle, then pull up thread around circle leaving tails on both ends. Trim inside (the square points) then iron edges. You can starch to keep the edge. Take out circle and gently tie ends but don't pull thread or you will distort circle. Hope I wrote instructions clearly. It should work.