We just had a class at our daytime guilt last month. Our presenter Lynne recommends Pelon fusible 911 interfacing. Cut the t-shirt apart, separating the portion you want with about a 2" margin if possible. Fuse the t-shirt to the fusible interfacing following manufacturers directions, be sure to use a teflon pressing sheet or parchment paper so the t-shirt image is not damaged. Trim to the desired square or rectangular shape. Lynne then works on a design wall (or floor) placing prepared t-shirt blocks in vertical rows. Use 100% fabric of your choice to add sashings/coping strips, unifying your vertical row widths.