Big T wrote: ↑June 3rd, 2021, 9:46 pmClamps and squares work great to keep everything squared up but they do very little to stop it from warping. The best way to weld it is using very short stich welds and letting it cool off completely before you make your next welds. It takes a long time to do it this way but it's the only option that you have when working with thin material. If you're asking about the best way to keep the box all squared up, it would be to tack together as many panels as possible before you start welding everything up.