Put it over a gas burner, bbq. or heat slowly in an oven and cook a steak, sardine, egg, piece of salmon, caramelise vegetables etc. The wetter the food the more it attracts salt out of the slab.
Chill it and use it as a platter for sushi, sashimi, carpaccio, steak tartare, gravadlax, smoked salmon…. the salt is antibacterial, so nothing nasty will infect it. It just needs a scraping for a clean.
Just a note on salt while I am on a roll. In American recipes in particular kosher salt is often called for. Kosher salt is rock salt or under ground saline water reserves evaporated for salt. Himalayan salt or Murray river salt, mentioned in the previous post, could be classed as kosher salt as they have not come from sea water (where there are many pollutants).