Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper for easy cleanup.
Pat the red snapper fillets dry with paper towels. This helps ensure a nice texture.
Place the fish fillets on the prepared baking sheet. Drizzle evenly with olive oil.
In a small bowl, whisk together the lemon juice, minced garlic, chopped parsley, chopped dill, salt, pepper, and optional red pepper flakes.
Spoon or brush the lemon-herb mixture evenly over the top of each red snapper fillet.
Arrange the thin lemon slices on top of the fish.
Bake for 12-15 minutes, or until the fish is opaque and flakes easily with a fork. The exact cooking time will depend on the thickness of your fillets.
Remove from oven and let rest for a minute before serving.