This method can be used for a small amount of oysters or a case!
Crank the oven to 425 degrees. Fill a baking pan halfway with rock salt or dried beans/legumes. This prevents the oysters from wobbling over.
Rinse the oysters free of mud and sand and set them aside. Do not dry— in the hot oven, the excess moisture will create steam that loosens the hinge muscle, making the oyster easier to open.
Place pan in preheated oven until the rock salt is crazy hot, about 15 minutes.
Place the damp oysters, deep-cup-side down, on the hot rock salt. (Don't overcrowd, as they need air circulation.) Return pan to oven to roast until the tension on the hinge seals is released and the oyster is slightly open, 6 to 8 minutes. Discard any that do not open at all.
Working one by one and using a folded kitchen towel, hold each oyster level (so you don't lose any liquid) and open with an oyster knife (or, in a pinch, we've used a paring knife, with care).
First, hold the knife curved-side down, tracing the upper shell, cutting the adductor muscle, and removing the top shell.
Then go curved-side up along the bottom, again severing the adductor. Many oyster knives are gently curved in order to follow the shape of the shell. It is an easy process.
Use the oysters to prepare Creamy Oyster and Potato Chowder.