If that's all you need, pick a substrate..... PVC, Cor-X, MDO, etc and cut it out on a band saw or a jig saw.
Cut the substrate into 8 equal squares, tape it together and cut them all at the same time, but go slowly and let the blade do the cutting, not you pushing them through. There's a method to cutting multiples at once and slowness is the key element. And wear eye protection.