1. Lay tofu block on a dry surface with the shorter sides on the left and right. Vertically cut into 1⁄2-inch-wide pieces. Horizontally cut each piece into 4 smaller pieces.
2. In a medium bowl, combine soy sauce, oyster sauce, cornstarch, sesame oil, ginger, and red pepper flakes. Whisk until cornstarch has dissolved.
3. Bring a skillet sprayed with nonstick spray to high heat. Add tofu and sprinkle with salt. Cook until golden brown, about 6 minutes, gently flipping to evenly brown. Transfer tofu to a large bowl and cover to keep warm.
4. To the skillet, add stir-fry veggies, broccoli, and garlic. Cover and cook until hot, about 5 minutes. Give the sauce mixture a stir and add to the skillet, along with the tofu. Cook and stir until sauce has thickened slightly and tofu is hot, about 3 minutes. Dig in!