Preheat oven to 350 degrees F. Line a baking sheet with parchment paper or spray with oil.
In a small bowl, combine the minced garlic, lemon zest, chopped thyme leaves, and chopped rosemary. Mix to combine.
Using paper towels, gently pat the trout fillets dry to remove excess moisture. Arrange the fillets on the prepared baking sheet, skin side down.
With a pastry brush, brush olive oil over the flesh side of the trout fillets. Season each fillet with the sea salt and coarse ground black pepper.
Spoon the garlic, lemon, and herb mixture evenly over each fillet and spread it out to coat the surface. Top with two lemon slices per fillet and 1 tablespoon of the butter.
Bake for 12-15 minutes, until the internal temperature of the trout is 145 degrees F. Thicker fillets may need closer to 17 minutes until they’re cooked through.
