If you use flannel again, pre-wash but only on your permanent press setting. The hot water may have shrunk it to the point teh fibers will never go back to their original or almost original state. I would go so far as to throw it in teh washer again on teh pp cycle, dry on the pp cycle, and remove immediately.
I'm sorry, but I never use hot water to wash anything but my bath towels. Too risky.