Cutting on foam is ok if you're working in the same area a lot but I'm currently moving about a frequently and the foam takes up too much space in my van.
Consequently I use two sawhorses and put two eight foot long bits of 2x2 over them. Then some four foot lengths going across the long lengths.
Doesn't take much space up, my CTM extractor fits underneath and its flat enough.
I can move the cross pieces about to alter where its supported.
Plus every site I work on has a few bits of 2x2 that I can use for free, even on the sites that use the nice foam, they don't just give it away.
Just another option.