I'd cut muslin blocks (or a background color of your choice -- solid red and/or blue?) about 15" square. Then use the suggestion to spray baste the blocks to the background fabric and buttonhole stitch them, using your machine. You'd protect the beauty of the "finished" blocks you have, they'll float on the background fabric so size differences won't be as noticable. What fun you'll have. The finished blocks will make a lap throw about 45x60 before you add borders. If you can find a couple fabrics similar to that in the blocks then sew a narrow (maybe 2") and a wider 4" border in another color. A narrow black border on the inside would be a great way to have the colors stand out too. The blocks will tell you want they want you to do.