There are 6 squares with light grey as the background, and 6 more with black as the background. I created them 6 at a time. I just laid them out as you see here. No measuring, really. I just make a guess at each piece, arranging them quite at a whim. As I sewed 2 pieces together on my machine, I then ironed it and squared the edges with my ruler, mat and cutter before connecting the next piece. It is alot of up and down from the machine to the ironing board, then the cutting mat, but it really didn't take too long.