as a longarm quilter I have received many different backings. Fat quarters, wide strips 6 inch, just got one of 5 inch squares will be interesting. I have one of mine that is 2 yrs of 2 different fabrics with 2 inch strips sewn together in the middle to make it long enought. I have see a large pannel with borders around, I tell customers I cant guarentee centering this. I have seen left over blocks. so anthing goes as long as it squares up. If lots of seams on the outside edges, needs stay stitching to keep from unravelling.