'Design your custom maze puzzle box in Fusion 360' - Stuck

Hello, please could someone help me complete my custom maze puzzle box in Fusion 360?

I am stuck at where you create the notch (13:34):
(https://youtu.be/Q2mTf-L5rNE?t=815)

I have "Auto Project Edges on Reference" turned on in preferences, and am looking directly at the sketch.

I've attached my file below as an F3D and would be grateful if someone could have a look for me.

Puzzle Maze v1 - Help.f3d 513 KB

Thanks. 🙂