Irishrose, I don't need to do anything to the back of my applique. I leave the Wonder Under paper in place until I am ready to put the applique onto another piece of fabric. Usually I have appliqued it onto a block and the block is what has the Wonder Under applied to it. If I am going to applique that block to a larger piece of fabric, then I peel the paper off the Wonder Under and press it down. If the block is totally finished and ready to sew into the quilt top, I leave the paper alone. When I sandwich the quilt then I peel the paper off and press it onto the batting.The wonder Under is so light weight that it is hardly more than a stiff starch or a spray on basting. I find it gives a wonderful feel to the fabric and makes it much easier to work with. I hope this made sense to you. Some of the appliques in my current quilt have several layers of fabric and therefore several layers of Wonder Under, but I'm not cutting the back fabric out of any of them. I may add extra batting to some of them for a more heightened raised effect . Since there won't be any quilting through the actual appliques themselves, the additional fabric thickness will have no effect on that.