1. Fill a large bowl with room temperature water and stir in 1 tablespoon of cornmeal. Place live oysters in the water-cornmeal solution for at least 4 hours or up to 24 hours; refrigerate. As the oysters filter the water, they will take in the cornmeal grains and spit out any sand that they contain. Leave the oysters refrigerated in the water-cornmeal solution until they are shucked.
2. Spread an even layer of rock salt in a large, rimmed baking sheet. The rock salt will prevent the oyster shells from tipping as they bake. You can also use a large crumpled sheet of aluminum foil in place of the rock salt.
3. Fold a thick kitchen towel into quarters and hold it in one palm as protection for your hand from the oyster knife blade, in case it slips as you are trying to pry open the oyster. For extra protection, wear a cutting glove (available at kitchen supply stores) in the same hand that is holding the towel. In the towel, place one oyster, hinged end out and flat side up, and then squeeze it firmly. Using the work surface to anchor your hand, carefully and firmly pry the pointed end of the oyster knife into the small hole at the tip of the hinged end of the oyster. Gently and firmly rock the knife back and forth while pressing it into the hinge. Continue to press and turn the knife until the hinge pops. If you do not have an oyster knife, you can use a flathead screwdriver.
4. Continue to slide and turn the knife as you work your way along the lip between the two shells in order to pry the oyster open. Angle the knife toward the top flat shell, taking care not to puncture the oyster inside. Slide the knife along the top inner side of the shell to sever the membrane that connects the oyster to the shell.
5. As you loosen the top shell, pull the two sides of the shell apart to expose the oyster. Use the knife to fully loosen the oyster from the connective membrane on top and below the oyster. Be careful not to tip the shell so that the oyster and oyster juice remain in the “cup” of the bottom shell.
6. Use the knife to slide the oysters and juice into a bowl. Discard the top flat shells. Thoroughly wash and scrub the bottom “cupped” shells. Dry the “cupped” shells and place them on the baking sheet with rock salt.
7. Spoon one oyster back into each clean shell. If eating oysters raw, they can be served at this stage with lemon wedges and hot sauce. If baking the oysters, top each oyster with ingredients and bake as directed.