Steps
1. Preheat the grill to medium-high heat.
2. In a small bowl, mix together the olive oil, minced garlic, thyme, rosemary, salt, and pepper.
3. Place the mackerel fillet on a large piece of aluminum foil.
4. Brush the olive oil mixture over the fillet, ensuring it is evenly coated.
5. Arrange the lemon slices on top of the mackerel.
6. Fold the aluminum foil to create a packet, sealing the edges tightly.
7. Place the foil packet on the preheated grill and cook for 8-10 minutes, or until the mackerel is cooked through and flakes easily with a fork.
8. Carefully open the foil packet and transfer the grilled mackerel to a serving plate.
9. Serve hot with your favorite side dish.