I recently purchased a Zing Orbit and I’m quickly learning how to use it with Sure Cuts a Lot. However, I’m struggling a little with the 15″x15″ cutting mat that came with the device. The mat was rolled up in the box and I’m having trouble getting it to lie flat. I’ve tried placing it under heavy books and rolling the opposite way to take the bend out of it, but it’s not very flat and even has a little warp to it. How flat does the cutting mat need to be to work properly? Can you recommend ways of making it flat? Thanks!