Download and print our Fabric Dahlia Templates (be sure the Adobe Reader's page-scaling setting is set to "none"); then cut out one template along the solid lines. The PDF file contains several sizes; print the page that has the one you need.
For the bridesmaid corsages, we used the second largest template and 5-by-27-inch fabric.
Cut your fabric into a long rectangle of the appropriate size. Fold the long edges of the fabric together, then fold the strip accordion-style. Pin it in place, and use the stencil to cut out the petals.
Knot your thread, and sew a running stitch 4 or 5 inches into the length of the fold, then pull to gather the fabric. Curl into a small coil, and stitch to anchor. Repeat in short stretches, curling the fabric around itself and anchoring it as you go. When you reach the end, stitch to anchor the coil. Use your fingers to shape and fluff the petals.