Combine olive oil, lemon juice, lemon zest, minced garlic, chopped herbs, salt, pepper, and red pepper flakes (if using) in a large bowl. Whisk thoroughly to emulsify the oil and lemon juice.
Place chicken breasts in a resealable plastic bag or shallow dish and pour the marinade over them. Ensure each piece is thoroughly coated by massaging the marinade into the meat.
Seal the bag or cover the dish and refrigerate for at least 2 hours (ideally overnight). Turn the chicken occasionally to ensure even marinade distribution.
Preheat your grill to medium-high heat (approximately 375-450°F).
Remove chicken from the marinade, allowing excess to drip off. Discard the used marinade.
Place chicken breasts on the preheated grill and cook for 5-7 minutes per side, or until the internal temperature reaches 165°F at the thickest part.
Transfer the grilled chicken to a clean plate and tent loosely with aluminum foil. Allow it to rest for 5 minutes before serving.
Slice the chicken against the grain if desired and garnish with fresh lemon slices and additional herbs.