Cut tofu into ¾-inch cubes and pat dry, then sprinkle with salt. Place the remaining 2 tablespoons cornstarch in a large bowl. Add the tofu; toss gently to coat. Heat 1 tablespoon oil in a large nonstick skillet or wok over medium-high heat. Add the tofu; cook, undisturbed, until browned, about 3 minutes. Gently turn and cook, stirring occasionally, until browned all over, 2 to 3 minutes more. Transfer to a plate.