I made a large twin quilt for the hubby from denim squares cut to 6". I made the top rag style and backed with flannel and no batting. I did some fmq in each square....just a bit to secure the top to backing. It turned out great and hubby loves it. I would cut as large of squares as you can get without wasting fabric. Anything larger than a twin will be very heavy to deal with at the sewing machine...and the washer! Can you imagine pulling a queen sized wet denim quilt out of the washer!