I used flannel scraps once to piece the back of a puff/biscuit quilt. Did not preshrink or wash flannel. Has been washed many times since the 90's and is still intact. I am sure the makeup of today's flannel is nearly the same...but I think if was using flannel today I would definitely stay stich the edges {if it was new}, but I would wash in COLD water and let it air dry anywhere BUT a dryer!