If you want to use this method, I found the tools on line and the back is 9.5" and the center peice is 7.5" so that is a 2" margin all around the batting to allow for folding as shown on the video. I am making mine 12.5 and 10.5 and see
how it works. Have a lot of print materal I want to use in larger peices of 10.5" and backing and quilt that rather than the strip method