Many appliqué patterns contain circles, and the centre circle in Mariner's Compass and Dresden Plate blocks is often appliquéd as well.
With this set of large heat resistant circles by Karen Kay Buckley you will make perfect circles that you can appliqué by hand or by machine. The set contains 10 different sizes of circles, ranging from 2,25 inch to 4,5 inch. The set contains 2 circles of each size, so 20 circles in total. Cut out a circle with a seam allowance. Baste with a small running stitch in the seam allowance, and pull the thread tight around the template. Apply some starch or sizing to the seam allowance and put the iron on top, until the fabric is dry. Let the fabric cool, remove the template, pull the thread to make a perfect circle that you can hand or machine appliqué. If you do not have starch, a little works well too.
In the YouTube film below you can see a demonstration of the perfect circles.