I did a bunch of hearts on a quilt once this way: Trace the heart onto muslin or a fabric that matches your finished heart. Put it, right sides together onto your heart fabric and sew. Carefully cut a slit in the backing fabric, and turn right side out. Press carefully, being sure to keep the backing from showing at the edges. Applique as usual. This technique worked so well for me and the extra layer/seam on the edge wasn't a problem. I got the nice shape that I wanted, even hand-appliqueing with blanket stitch. Hope this works for you!