I just finished two lap quilts with a fleece front and a flannel back. I included batting and they are really warm. I was aiming for warmth and durability. They turned out great.

Yea I love flannels especially on the back of quilts for warmth. Just make sure you wash it first for shrinkage.

I have read that you may need to wash and dry 2 or even 3 times before using because the shrinkage is so great. Maybe it would not be a problem if it's flannel on both sides, but I'd be very careful if you have cotton on the front and a flannel backing...different shrinkage. Good luck!

I just finished 2 flannel quilts and they came out very nice. I didn't use any special methods - just put them together as usual.

I think you can get into a debate about wash/no wash that would last for hours. It is a personal preference. I prefer to "not". I just completed two large Brickyard flannel quilts for Christmas giving. I did not wash either of them until after they had been completed. I used quilter's flannel (the expensive stuff) for the front and back of the bricks and JoAnn's marble pattern ($2.49/yd) for the batting. After washing/drying in a laundromat both quilts looked great and with 1/2" seams ragged at 1/4" - they were full and fluffy. I used to hate flannel, but not any more .... now don't get me started on trying to use a flannel panel print for the center of a baby quilt. UGH!

I don't for rag quilts.

Two layers of flannel are nice and warm. I have done this with no batting.

I have an old Pfaff 1222E that l use when piecing flannel quilts. All the other machines in the herd can't do that without a walking foot.

I wash flannel 2-3 times in hot water and dry on hot.

Are you speaking of magic sizing?