I put flannel on the backs of quilts and sometimes on the front of baby quilts. Flannel likes to stretch and fray a little so keep the pieces larger and the pattern simple (think Warm Wishes, Rail Fence, framed square). Quilt it fairly closely and make the seams a little wider so they don't pull out. I don't like to tie flannel quilts for the same reason. The ties may tear out as the quilt is washed or pulled. I have also mixed flannel and cotton and that will work too.