Styrofoam can be cut and shaped into lots and lots of shapes. you can carve it with sharp razor blades, electric carving knives, hot wire cutters, saws of various types and you can also use your fingers.
Home Depot sells Styrofoam building insulation is 2x8 sheets. I try to always have a couple of sheets around. They are just that handy. We use them for building models, adding spacers to the counterweight system and more.