Are you only using Minky? I use it all the item for rag quilts while it does not rag it curls and is still cute. Most the time I use one layer Minky and two layers of flannel. You need a wider seam about half inch from the edge and you need to use a ball or stretch needle. I have good luck using 9 in squares without spray basting. If both top and backing are minky use one layer of flannel in the middle it will hold them together and minimize the slide while you sew. I do each square with an X in the middle to stabilize them. Also lengthen your stitch to about 4 to 4.5 in length.