Drain tofu paper towels for about 45 minutes. Cut block into 1/4-inch-thick slices; cut slices in half. Arrange slices into a single layer over dry paper towels and sprinkle 1 tablespoon flour on top. Flip slices over and sprinkle with remaining flour.
Heat oil in a skillet over medium-high heat. Saute tofu until light brown, 3 to 5 minutes per side. Add sesame seeds and toss with mustard, using a rubber spatula to avoid breaking tofu slices. Serve warm.