I have made three string quilts. My first one I used no foundation and only a kite shape to begin with and added strings on both sides. My 2nd and 3rd, I used fabric that was really thin and a pale neutral color as my foundation. I cut pieces of it into about 6.5 inch size and then began sewing on strings. # 2 I used a common fabric for my center starting strip so that made the design in the centers look joined. My 3rd, I again used really thin fabric and sewed selvedges. I did that one as QAYG. I really like the idea of using the thin fabric (muslin would be great, too as Lynnie said) because I hate ripping off the paper. I just used a lightweight batting and they were just right when quilted. After the strips were sewn on and foundation covered, I re-trimmed to the size I wanted them to be. You could choose any size for yours. Just cut out oversize pieces of foundation to start off with.