If using the oven, line a rimmed baking sheet with
aluminum foil, scrunching up the foil into irregular
mounds to help hold the oysters in place. Place the oysters on the foil, cup-side down, arranging them so they are as flat as possible so none of their liquor spills out when the shells open. (If using the grill, place the oysters directly on
the grates once the grill is up to temperature.) Roast the oysters in their shells until the shells have begun to open and you can see some steam escaping, about 8 minutes.