I have just finished 2 rag quilts for my granddughters made of flannel with batting in between. I pre-washed the flannel and it shrunk considerably in width but not length. I really enjoyed the process and found it most forgiving! Very weird sewing the seams on the front of the quilt...had to unpick a few blocks that I sewed "incorrectly" with seams "inwards"! The end result with the flannel on front and back is terrific...very warm and snuggly. I heartily recommend using flannellette for the top and bottom.
The first quilt is yellow floral and plain pink blocks with a ladybird backing, and the second, a lemon gym shoe and plain mint green blocks front and back. Colours were a bit tricky to match but I got them on special so wasn't going to complain and as it has turned out...I'm very happy with them. I did invest in an expensive pair of rag snips for the second one as I found that the generic snips I used for the first one blunted very very quickly trying to cut through all those layers. The snipping for each quilt took me about 2.5 hours!
Have fun...look forward to seeing your pics of the finished product!!