I have a set of Karen Kay Buckley's "perfect circles". If I need a lot, I draw around them onto template plastic (the kind you can iron). Then I cut the fabric circle about 1/4" larger, baste all the way around about 1/8" out using quilting thread, pull to tighten, and knot off. I iron this circle, sometimes using spray sizing, cool, and slip the plastic piece out. Then I applique the circle down using silk thread and a straw needle.