The quilt as you go (QAYG) method will work, but will look best if you have some similar lines in the original quilt. For example, if you have a small inner border or sashing, adding a QAYG "bridge" or connector strip will look ok. I did this a while back and the inner border was 2" finished. It really looked too big, compared to the QAYG "bridge" so I simply added two rows of quilting to that border, making it look like it was three smaller strips. Unless they looked closely, no one noticed that I did this. Good Luck!