Lay the foam down on a garage floor, lay your plywood (what-have-you) on the foam, lay your track across the wood (where you want the cut) and go.

As long as you make sure the depth of your cut doesn't pass all the way through the foam, you're good. (And a 1" margin for error should keep you from sparking the saw on the concrete floor.)

If you're clever, cut the 4' x 8' sheet of foam (with a long X-Acto knife) into 4 pieces: 4' x 2' each. Duct tape pairs of them back together and you can fold up your foam like a gym mat. Note: make sure the tape is on the floor-side, you don't want to cut through duct-tape.

Add a portable drill & driver combo and your woodworking journey has begun.

(Me, I added a jointer, planer, table saw, routers, built a workbench, etc. You need a lot of clamps. Got rid of my miter saw—kinda dangerous and I just didn't need it. To be sure the table saw is dangerous too, but the miter saw is stealthily so—seems undangerous for the longest time and then‚ bam!)

Well there is also a chainsaw, but that is solving a different problem. No one uses chainsaws for woodworking, only those people carving stumps.