I had some left over flying geese blocks from a quilt I did. But I did not have enough to make the border out them entirely....so I grouped them and put groups of 1, 3, and 5 evenly around the whole quilt with just a small print fabric in between....and I did put a narrow border between this outer border and rest of the quilt. It turned out nice! umm...to make it rectangular, I would maybe put a small border at the top and a small border at the bottom....add your left over blocks at the top and bottom and then put another small border all around the whole quilt and bind using the same fabric as that outer small border? I think that might work!