Prepare a charcoal fire using about 6 pounds of charcoal and burn until the coals are completely covered with a thin coating of light gray ash, 20 to 30 minutes. Spread the coals evenly over the grill bottom, position the grill rack above the coals, and heat until medium-hot (when you can hold your hand 5 inches above the grill surface for no longer than 3 or 4 seconds). Or for a gas grill, turn on all burners to High, close the lid, and heat until very hot, 10 to 15 minutes.

Meanwhile, place the trout on a clean work surface and season inside and out with salt and pepper. Equally divide the lemon slices and herbs among the trout cavities.

Place the stuffed trout on the grill, heads facing in one direction. Grill, covered, until cooked on one side, about 5 minutes.

Uncover the grill, and flip the trout over (simply roll them over with a metal spatula). Cover, and continue cooking until the trout is done on the second side, an additional 3 to 5 minutes.

To serve, remove the trout to a warm platter and drizzle with olive oil. Garnish with the fresh herbs and serve immediately.