Last month, one of my favorite blogs "A Girl and a Glue Gun," posted a fun marble maze. While in TN, I got to work craft-lifting it. I am adding a few more details that I find might be helpful.
Step 1: I use a rotary cutter and a self-healing mat to cut two 12 1/2" fabric squares. It can also be helpful to chalk a 1/4" line along the outside to save space for the seam.
Any other thoughts?
Happy Belated 4th of July!