Cooking bass in a bed of salt not only turns out moist, flaky fish, but it also makes for a striking presentation.
Preheat oven to 400 degrees. Beat egg whites by hand or with the whisk attachment of a stand mixer until soft peaks form. Use a rubber spatula to fold in salt until combined.
Season inside the fish with pepper and stuff with half of the lemon rounds and 3 sprigs thyme. Spread a 1/2-inch-thick layer of the salt mixture on a parchment-lined rimmed baking sheet to form a bed for the fish. Lay fish on top of salt. Season outside of fish with pepper. Place remaining lemon slices and thyme on top of fish. Pat remaining salt mixture over top to cover entire surface, including head, leaving tail exposed.
Bake for about 35 minutes. Crack open salt crust using a fork or spoon, exposing the fish. Transfer to a serving plate.