To reverse applique you would have your two pieces of fabric. Transfer your main shape to the right side of the top layer of fabric. Pin the two layers together on both the inside and outside of the shape or marked cutting line. Carefully cut along the marked line on the top layer only. Then, using needle-turn applique method turn under the seam allowance of the inside shape and stitch to the bottom layer of fabric. Continue until you are done with the inside shape and then stitch the outside raw edge in the same manner with needle-turn applique to the bottom fabric. Remove pins and press.