Cut three slits, about ½ inch deep and 2 inches apart, diagonally in the sides of each fish; don’t cut down to the bone. Arrange the fish in one layer in an ovenproof casserole.
Combine the soy, sesame oil, and garlic in a small bowl. Stir well, and spoon over the fish, making sure the mixture seeps into the slits. Let the fish stand, loosely covered, at room t