1. Prepare the Chicken Breasts: If your chicken breasts are very thick, you might want to pound them to an even 3/4-inch thickness. Place each breast between two pieces of plastic wrap and gently pound with a meat mallet or a heavy pan. Once even, pat the chicken dry with paper towels.

2. Whisk Together the Marinade: In a medium bowl, combine the olive oil, fresh lemon juice, chopped fresh parsley, chopped fresh oregano, chopped fresh thyme, minced garlic, salt, and black pepper. Whisk everything together until well combined.

3. Marinate the Chicken: Place the prepared chicken breasts into a large resealable plastic bag or a shallow dish. Pour the lemon herb marinade over the chicken, ensuring all pieces are thoroughly coated. Seal the bag or cover the dish and refrigerate for at least 30 minutes, or up to 2 hours. Do not marinate for longer than 2 hours.

4. Preheat Your Grill: While the chicken is marinating, preheat your outdoor grill to medium-high heat (about 400-450 F or 200-230 C). Clean the grill grates thoroughly with a wire brush, then lightly oil them with a paper towel dipped in a little cooking oil.

5. Grill the Chicken: Remove the chicken from the marinade, letting any excess drip off (discard the remaining marinade). Place the chicken breasts directly on the preheated, oiled grill grates. Close the lid and grill for 6-9 minutes per side, depending on the thickness of the chicken.

6. Check for Doneness: Use an instant-read meat thermometer inserted into the thickest part of the chicken breast. It should register an internal temperature of 165 F (74 C).

7. Rest the Chicken: Once cooked, transfer the grilled chicken to a clean cutting board or platter. Tent it loosely with aluminum foil and let it rest for 5-10 minutes.

8. Serve and Garnish: Slice the chicken against the grain, if desired, or serve whole. Garnish with fresh lemon slices and a few sprigs of fresh herbs.