We needed more kitchen workspace so I built a 24x26 inch cutting board that fits over the oven when not in use.
I placed two planks of wood underneath to act as rests so it locks on to the top of the oven.
Obviously when the oven's rings on I can't leave it there, but thermally can I put some kind of layer underneath for thermal prevention.
Maybe a welding blanket of some kind. No direct experience, so just guessing.
I'm really confused. You want something that's going to allow you to leave a cutting board on top of running burners?
Silicone might protect it from scorching, but assuming you used food-safe PVA glue to join the board, it melts at around 120 degrees and your board will fall apart regardless.
Constant, extreme thermal cycling will also dry out the board and warp it in a hurry.