Suggestions On How to keep food warm for a buffet at home?

Thats a good way with things on hand.
You use those materials just to preheat the
cold ice chest walls. Should feel like a nice
warm cozy place when you stick you hand in there.
Then when you pack it up to go, make sure
all the food is hot. I mean hot, not warm, or
just perfect temp to eat. Like, right off the
stove or oven, hot. By the time you transfer to sterno
chaffers, should be perfect.

Interesting, especially with sand, Ive never done it that way,
always took the preheat materials out and relied on the
thermal action of hot food in an enclosed environment.
I may try it that way sometime to see how it works.

Well sure, Cambros are the best, but as was indicated, only frequent use justifies their expense--couple hundred bucks a pop. You can get a full sized igloo cooler that fits hotel pans for 70 bucks,
plus being an ice chest, has a zillion other uses. Of course the other option is to just rent a couple Cambros (thermal boxes) for the weekend, and you dont have to store them.

Is it even LEGAL to do that? Anywhere?

Still processing California to Virgina......

You mean by CAR??

Well, boiling water poured IN can wreck it too, doesnt take
much direct heat to melt that stuff. I put the pot in there...
on a thick layer of dish rags or potholders. Its the steam that
preheats the "space" not the surfaces. IMO, this method
works much better in plastic cambros, than with styrofoam.

Oh ok, my bad JAY. That makes more sense of course.