1.5 inches is rather small IMHO. I'd make one block first before deciding.
Anyway, Fat quarters are fine. However, you can't easily do Eleanor Burns method with it. I ended up using rulers to cut to sizes needed. When you are ready to work the project, put in n audio book and press and press. Then continue listening while cut, cut ,cutting. Don't expect to get the cutting done all at once. Also, don't do it while watching TV or you will cut yourself.