Big thanks to Tim Anderson for taking the action shots.
Step 1: Cut Your Stencil
The low-tech version would be to print out the design in reverse, tape it to cardboard, and go nuts with a box cutter or Xacto blade. But that's another story for another Instructable and you're smart and clever enough to figure it all out, right?
After you've made your cuts, put all the pieces back together. This is how you're sure the placement is right.