So after years of having my collection in storage, I decided to finally make a Marklin Z layout. I've settled on a track plan, set it up and run it on a temporary basis and am getting the materials to build the layout table.

I plan on using XPS foam on top of plywood for the table. I'll be using IBL cork roadbed and Marklin track. I'm pretty sure the best way to attach the road bed to the foam is with Styrogoo or something similar (anything that won't attack the foam). But what's the best way to secure the track to the roadbed? (I do not plan on ballasting the track.) I have the Marklin track nails, but I'm concerned they won't grip the foam. I note that screws are available for the Marklin track. Will those grip the foam? Or should I plan on glueing the track to the roadbed?

The nails will not grip the foam. You could just use some more plywood & cut out some track layout plans. Glue that down & nail to that.

That is effectively what I did with my first layout. Plywood base board & plywood track bed, but with tapped & threaded spacer tubes between the plywood. Tough as nails & nothing moved, but it did take a long time to build. But I would be happy to do it again as it was bullet proof.

All the gaps & for landscaping base I filled with expanding polyurethane foam. Which I used for my current layout, but slightly different track base design.