01 - Preheat the oven to 400°F. Lightly grease a baking dish sized to fit the fillets in a single layer.
02 - Combine olive oil, garlic, lemon zest, lemon juice, thyme, parsley, sea salt, and pepper in a small bowl.
03 - Pat halibut fillets dry with paper towels and place them evenly in the prepared baking dish.
04 - Brush the marinade evenly over each fillet, coating thoroughly.
05 - Place thin lemon slices atop each fillet.
06 - Bake in the preheated oven for 15 to 18 minutes, or until the fish flakes easily with a fork and is opaque throughout.
07 - Sprinkle extra chopped parsley over the fillets and serve immediately.