I am making barn quilts and I take a quilt pattern and draw it onto graph paper which is 1/4" = 1" block. It would have to be 12-1/2" square to finish at 12". I would really like to see a wall hanging made. Anyway, if you have the graph paper, draw a square 12-1/2" square. That would be 12 and 1/2 blocks each way. Then draw from corner to corner each way, then draw a grid of 4 each way. Start in the middle and draw your small square. Then continue to draw it out. If you need help, I can do it for you. Just pm me. By the way, I think this is called triple star.