Tee-shirt quilts are easy to make because they have such big pieces. First you cut the front of the tee shirt bigger than the finished block size. Then you use fusible interfacing on the back of the whole piece, being careful not to melt the design on the front. I use a teflon applique pressing sheet under mine. Make sure it is fused on well. Then and only then, cut the teel shirt to the size block you want. There are books with ideas for layouts but mostly, you just start putting them together. You can use shashing between the blocks or just stitch the blocks together if you have enough to make the quilt the size you want.