If you are using cotton fabrics, you can put a piece of batting between your squares, cut your batting at least 1 in smaller than your squares and use a 1/2" seam and clip to seam. You can also use a piece of flannel in the middle. Some people, when making a rag quilt out of flannel fabrics don't put any batting in it because it will be warm enough. I made a flannel one, and used warm and natural batting in the middle, used 1/2 in seams. Sandwich your batting, centered between your squares, stitch an x across.