You can make your own circles out of card stock, water color paper or a cracker or cereal box. I use a compass to draw my circle then carefully cut it out. I cut out my fabric circle with a seam allowance and then do a loose running stitch around the edge. Then I use my cardboard circle and place my fabric over it, centering it and pull that running stitch tight. Makes a perfect circle. Press it real good with the cardboard still in it then take the cardboard out, give it another press and spray it with starch. Then press again. Perfect circle everytime. It is how I made this quilt:
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