Does anyone know a perfect way to cut 45 degree angles on edges of foam?

[Graphic Jordan]

Thanks for the help guys. I ordered an Exacto Mat Cutter it cuts 90 and 45 angles. I will also look into that drywall aluminum angle.

 

[Pilot]

Somehow I completely missed the fact that you're using 4mm foam. Reading is fundamental! :lol

The mat cutter is probably going to be way more effective on the thin material than my redneck system. Still works a treat on the thicker stuff though.