I have made three rag quilts with recycled denim on the back, flannel on the top.
The jeans took time to cut up, but I have fun with pockets and other features. The flannel I first ripped into long strips, them stacked and cut into squares 4-6 layers at a time. It went quite quickly.
I did not use any batting or middle layer, as the quilts were heavy with the denim. I did not X the squares.
The best tip I heard was to buy spring loaded scissors for the snipping. I used regular ones for the first quilt and my hands were very sore.