If you use wonder under and iron it down I don't see how you will be able to turn it under. I Put freezer paper on the back of my fabric and (cutting the freezer paper the exact size of the piece) iron it on the fabric and cut it out leaving a1/4 inch edge around it. That way I can turn it under as I go before I put the lasst few stitiches in I pull the freezer paper out. Marge