I thought you weren't going to use a backing. Did you change your mind? I think it will rag much better this way. Which side is going to be ragged? It will be pretty either way. I make mine with 2-3 layers of flannel, sew 1" seams, don't bother with x-ing through the squares unless they're really large. I also rag the edges after sewing a line of stay stitching.
When you do the ragging, get some spring loaded scissors. I makes a huge difference - your hands will thank you for them.