I usually select one of the fabrics in the quilt top and use it as a backing. Since it's usually 45" wide, I run the seams horizontally (side to side). I've also used some of the solid color, wide fabric from a local quilt shop, but prefer the front and back to match. Most of my quilts are queen-sized and quilted on a longarm. I never make scrappy quilts and seldom use pre-cuts as I prefer a more traditional look or blocks with tons of machine embroidery.