Welcome, sidmona. I use unbleached flannel as a backing for bedquilts and I hand quilt - it's lovely to work with! I absolutely agree though that you MUST pre-wash because it can shrink a lot! Ironing yards of flannel is not the most fun job in the world :? but if you have a tumble dryer, another lady on her - Pam - recently posted that a quick whizz through the dryer gets the creases out. Can't try it myself - no dryer!
K x