To cut steel flat bars to a specific length, you can use various tools such as a hacksaw, circular saw, or angle grinder equipped with a cutting disc suitable for metal. Measure the desired length accurately using a measuring tape or ruler, and mark the cut line on the steel bar. Secure the bar firmly in a vise or clamp to prevent any movement while cutting. Then, carefully follow the marked line and use the selected cutting tool to make a smooth and straight cut through the steel flat bar.