I don't think the bed wood and strips can be pre-assembled to the cross sills. It would be a lot of trouble (make that impossible) to get the wood under the bedsides angle strips and above the front and rear cross sills. The front panel also has to go under the wood. I believe the wood was originally coated with lampblack and linseed oil prior to assembly, not painted.
I think you're going to have to assemble it one board at a time, starting from the outside boards that slip under the angle strips that were welded to the bedsides. The angle strips also extend over the rear cross sill and the part of the front panel that have to go under the wood.
There were some later beds that had the bed wood painted body color (a fellow bolter has posted pics of bed wood painted body color), so if you wanted to go that way the bed could be fully assembled before painting.
Last edited by klhansen; 08/28/2024 1:36 AM. Reason: clarified