Season the inside cavity of each trout with sea salt and black pepper. Place 2 sprigs each of tarragon, parsley, and dill and then top with about 3 sliced of lemon in each trout cavity.
Line a large grill basket with lemon slices and place the trout on top of the lemons. Place more lemon slices on top of the trout and securely close the basket. (The layer of lemon slices on the bottom and top of the trout not only infuse the lemon flavor to the trout but prevent the fish from sticking to the basket.)
Place the fish basket on the grill and cook until the skin is nicely charred on both sides and the flesh is cooked through, about 6-8 minutes per side.
Transfer the trout to a platter and serve with the grilled lemon slices.