Soak the planks in water for at least one hour. Prepare the coals. When ready, lightly dry the plank. Brush one side of the fish with a generous coat of olive oil; if the fish has the skin attached, oil that side. Place the fish oiled side down onto the platter. Sprinkle the top with Cajun spices, mixed Italian herbs, paprika and garlic over the top of the fish. Juice half the lemon, slice the other half thinly. Evenly sprinkle the fish with oil and lemon juice. Finish off with sea salt and freshly ground black pepper. Top with the sliced lemon.