I have made 3 flannel quilts in the last several months, the last being king size. Two I backed with fleece and the king with 110" wide flannel from fabric.com. This is what I have found. I did not prewash because all were from kits, but before cutting I would starch very heavily (I make my own starch from sta-flo so I would spray until very wet) the back of the fabric and iron. I found that a good soaking and iron will take care of shrinkage and you don't get the ends all messed up and stringy like you do when you wash. I did pre wash the backing flannel because I knew I had enough and it was a dark color and I did not want it to bleed into the top after it was finished. Another thing I found was with the binding. The first 2 quilts I used 2 1/4" binding strips, they were too small but I managed. On the king it called for 2 1/4 but I increased to 2 3/4, worked much better. All my quilts had triangles they were a challenge. The heavy starching really helped there. HTH