Preheat the grill to medium-high heat.
Clean and gut the fish if not already done.
Rinse the fish under cold water and pat dry with paper towels.
Rub olive oil over the fish, inside and out.
Season the fish generously with salt and pepper.
Stuff the cavity with lemon slices and fresh herbs.
If using, add sliced garlic for extra flavor.
Place the fish on the grill and cook for about 10 minutes per side.
Use a spatula to carefully flip the fish halfway through cooking.
Check for doneness; the flesh should flake easily with a fork.