I bought 4 square Teflon Trivets to put underneath my kettle. They work great to protect the stainless tabletop from getting scratched and they also act as insulators to prevent the kettle from losing heat.
I have wooden stand that I built, and I use a ceramic floor tile that I bought for about $1 at Lowes. Lots of different sizes to match up with whatever diameter your brew kettle is. It just sits on the stand underneath my kettle, and it doesn't scratch the wood, so I would imagine it would work fine on Stainless Steel.
I chose this because it was dirt cheap, cleans up easy if you have a boil over/spill, and it insulates really well. For a stainless table, the only real concern I would have would be heat loss: the table will pull a lot of heat out of the bottom of vessel if it is not well insulated between the vessel and the table. A thin silicone mat may not give enough insulation, depending upon how big your heaters are. That will lead to longer heat up times and more electrical usage. I tend to build stuff to minimize heat loss, since that translates into less electrical usage.
Nothing here but I have scratched up underneath. It wasn't a particularly expensive table and I wasn't particularly concerned with it getting scratched. I am very careful with my kettles. My Herms ports/QDs are at an angle that is over the table and so even though I try to be neat and slip a towel under those I still get some minor dripping from time to time onto the table when disconnecting lines. Same thing on my whirlpool port.
You're gonna hate this answer, but I got a stainless cart and needed something to elevate one kettle to put the burner underneath,so I used a few bricks....
The reality is it won't scratch it much if I dont move them...
Maybe later I'll build a kettle stand outta stainless tube...for now it works!
I picked up 3’x4’ x1/2” Aluminium plate at a garage sale for $10, has rounded corners , so I’m not worried about it getting scratched or burned from my burners .