I've done it before. It's something you do for fun, not because it's a superior way to cook a steak. It's best to use a rock that's been kept dry...don't dig one out of the creek because it will most likely split when it gets hot.
I have a salt block that I use on a very irregular basis. I had some striped bass on it. That tasted amazing. It is best when the salt block is pretty hot to begin with.
Neat though. Should work great for toasting bread? Survival Skills: How to Cook Food on a Rock - YouTube
