Karen Kay Buckley Perfect Circles or otherwise if it's not the right size, I do what Lori wrote. Sometimes I use empty cereal boxes. If you need more than one of the same shape, it's worth it to invest in the Mylar (heat-resistant) template plastic because the regular kind will warp after ironing. Instead of Pigma pens, I have a template pencil. I bought it at JAF. It wipes off the template with a paper towel but stays when I need it to.
After I've drawn up the edges, I paint starch on them with a Q-Tip so it's nice & saturated and then press with a dry iron.