Preheat oven to 450°F and put a rectangular glass baking dish in the oven to heat up.
Sprinkle olive oil and salt the cavity.
Stuff the cavity with aromatics (lemon, garlic and oregano).
Rub avocado oil on the outside of the fish and sprinkle salt all over.
Take out the baking dish and place the fish on it; it will sizzle. Your smoke alarm may go off. Be ready.
Bake 15 to 20 minutes, until the fish flakes and is easy to open up and fillet.
Fillet the fish, squeeze the remaining half a lemon on top, and serve. (There are plenty of good videos online for how to fillet a fish.)