I made several rag quilts this Christmas, using flannel and a light batting. I found it was easier to start off with 9" blocks, and 8" batting blocks. This allows for the 1/2" seam allowance, and also, you can get four 9" strips out of each yard, making the math easy. My best advice, don't clip too closely to your stitching. You don't want to accidentally clip through and end up with holes in your quilt. Good luck!

I use a very small zig zag to put mine together.