Season the fish pieces with salt and pepper and dip in the remaining flour, shaking to remove the excess. Then dip each piece in the batter and coat well. Drain and fry a few pieces at a time, shaking the basket from the fryer to prevent them from sticking to the bottom. Cook for about 4 minutes. Remove the fish and drain on the rack. Sprinkle with salt. Keep warm in the oven while cooking the remaining pieces of fish. Serve with the sauce.