At least 3 fabrics are needed. Lay one down FACE DOWN, next two FACE UP, stitch your lines on the diagonal (this works best), cut ONLY the TOP layer between the two layers that are FACE UP.
I usually just wash, but be prepared for a lot of lint in the washer/dryer if you are using flannel. I have not had real good results with cotton (not as much fraying).
If you want a heavier quilt use 4 layers of fabric. You can get a different look by cutting the top 2 layers between every other stitch line and 1 layer the opposite stitch line.
Just remember you have to have your design open on an edge to start your cutting (it's easier). I used my needle to the far left and used the edge of my pressure foot for the width guide.
I was going to post a picture, but I can't find it anywhere!
Good luck!