When I did mine (click pic to see my blog post abut it):
I actually cut long strips of fabric from a toddler bed sheet that my son no longer used. I used this sheet as a base for the strips. This allowed me to not worry about my strips going wonky as the strip got longer, I just cut all my pieces slightly longer than the sheet base and trimmed it to the size of my original sheet base at the end. It was so easy.
Good luck!
Rachel