For a two-in-one entertaining trick, toss the pan drippings from the fish with quinoa or couscous. Side dish, done!
Strip enough thyme leaves from a few sprigs of thyme to measure 1 tbsp. In a medium bowl, mix the thyme leaves, the EVOO, 1 1/2 tsp. lemon zest, 1 tbsp. lemon juice, the garlic, kosher salt, coriander, crushed red pepper, and 1 1/2 tsp. black pepper for the marinade.
Stuff the remaining thyme sprigs, two-thirds of the lemon slices, and the parsley inside the fish. Place the fish on a rimmed baking sheet lined with parchment paper. Pour the marinade over the fish. Arrange the remaining lemon slices on top. Cover the fish with plastic wrap and refrigerate for at least 1 day or up to 2 days.
Preheat the oven to 350°. Uncover the fish and bake for 10 minutes. Turn on the broiler. Broil the fish until the skin is lightly browned and the fish is cooked through, 5 to 8 minutes. Carefully transfer the fish to a platter. Sprinkle with fleur de sel, if using, and black pepper. Pour any drippings from the baking sheet into a small bowl or pitcher to serve with the fish.
