I love making potholders from my scraps. My MIL prefers flannel ones, and they definintely get used. I use 3-4 layers of flannel.
One thing I do is to baste the back and batting together before sewing on the top. That keeps the batting from slipping around and bunching up.
One word of warning: If you combine flannel and quilting cotton in a potholder, it will shrink and warp. This is because flannel shrinks much more than cotton, even after a couple of washings. I have been told that in the "old days" this was sometimes done on purpose.