I use Minkee and Fleece all the time for backing. I sew a 5/8 to 3/4 inch seam, then I open up the seam and sew down both sides. There is no way to press this open and you can't pin it. It is very bulky if you don't sew it "flat." You can even make it a larger seam if you want. I use "lengthwise" because you want the "stretch" part of the fabric going across your frame. Don't try to overquilt, and make sure the nap goes in the same direction.