Only pillow case it if you aren't doing a binding on it. It's really better if you have a walking foot, makes a world of difference. My daughters first quilt she wanted fleece on the back, it was a block quilt so she did the SITD and then tied the rest of it. It turned out great, only a few tucks here and there. That would be your biggest issue doing the pillow case method with fleece and not having a walking foot. by the time you get to the end of the row, you'll probably have extra fabric and will end up with tucks or pleats at the end. My daughters last quilt, we sprayed it and stil did a few pins just to make sure it didnt shift and she was surprised to see no tucks or pleats when she used the walking foot. Good luck.