I welded my router frame up using a 90A SIP stick welder off ebay, as well as the professional MIG welders I had access to at my old work. If you cut the metal accurately, take your time positioning and tacking and have a large hammer and a grinding disc/cutting disc along with lots of patience then you can easily weld up an accurate frame, especially if you're planning on using epoxy for levelling. Secret is not to put too much heat into any one bit, so tack then move on to a bit on the opposite side and tack etc. leaving plenty of time for things to cool down.