You could make the outside stips 2.5 by 6.5 and the middle stips 1.5 by 6.5. Then your squares for the corners of the snowball block would need to be 2.5 to match up with the wider strips. I don't think you'll have much luck dividing into even width strips. 5.5 doesn't divide by 3. There may be a formula somewhere, but I don't know where.