Safe "Foam" for Tiger Salamander Enclosure?

I am currently building my tiger salamander a new, larger tank to live in. I would like to raise the base of this new enclosure to allow for some better mobility when it comes to him getting places and that would allow me to let him use an older hide I had purchased previously. He currently lives in a tank lined with EcoCarpet and has never had any issues (4+ years).

I was wondering if there was some kind of foam, sponge, or other substance I could place underneath the carpet that would be safe for him and (preferably) be fairly easy to clean out. My plan is to make his water areas more parallel to the ground as he typically struggles to get into the dish, to place a dug out section for him to burrow (currently a large plastic dish filled with dirt) that, again, would be more parallel to the floor of his enclosure, and allow me to use a previously purchased hide that has a decent sized drop from the entrance that currently causes him to struggle to exit (the reason it is not currently in his tank.)

Any recommendations would be highly appreciated. Thank you.

What about poret foam? It's safe enough for aquarium use, it doesn't come apart like the polyester foams do after a while so there's no risk of foam bits getting ingested, and it's super easy to clean. I would get a larger pore size (20 ppi) so it still breathes when covered. Plus they are virtually indestructible, it will last you ages!