Probably the easiest way to make it without a fixture table, would be to loft the pattern onto a table and then set and secure enough alignment stops to be able to tack weld the frame. Then take the frame off the table, set it on a known surface and then shim and clamp it for final welding. It would take way longer than using a fixture table, but with care, you can get the same or better accuracy. In the aerospace industry, we often build initial parts without hard tooling or jigs to under .010" tolerances, but it takes time and using both lasers and transits to set physical locations.
BTW…lofting that print would take probably well over an hour and a second person to get started.
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