I appliqued a bunch of hearts, using Heat & Bond Lite. I traced the shapes onto the paper side, then ironed it onto my fabric. I then cut around the shape, leaving about 1/4" to turn under. Clipped all curves, then turned the fabric under and pressed the edges, folding against the H&B, as a guide. THEN I removed the paper and just touched the turned edges, with the tip of my iron, to make them stick to the H&B edge. After the edges were neatly turned, I fused the hearts onto the blocks, then used a machine blanket stitch, to secure them.
After washing, the hearts aren't stiff, at all. They just have the feel of being a (very) slightly heavier fabric.