How do you weld a box-type part, with a six-sided seal and many ribbed plates in the center, as shown in the picture, and how do you weld the last side?

I'm not going to talk about the front, but the back can be welded in pieces, that is to say, divide the cover surface into large 4 to 6 pieces according to the grid lines of the grid, and just weld these large pieces to the box. Or, depending on your requirements, scribe the mesh lines exactly to the cover, and weld the plate through with high current so that the mesh is welded to the cover.