Start by laying the larger bottom panel in an open space, then slowly “dry” assemble it by laying the pieces where they go like a puzzle.
It should be fairly simple, large top and bottom panels, two side panels, the front baffle of course, the back panel mirrors the baffle just without holes in it, then the port pieces and bracing. Look at the inside view of the instructions and it gives the basic overview of assembly.
Also would be good to look at the stock photos on the GP website as you are dry assembling it.
I'm surprised GP doesn't have basic building instructions on a youtube channel in modern times.