I placed my bed on end with the tailgate up near the ceiling of my garage. I blocked it up and tied the bed so it was square. Then I assembled it standing up. It's a ton of work without crawling underneath it all day.

Mine also had two small holes in the sides on both ends. I put the cross member on the frame and checked it out because this is where my exhaust brackets were bolted to. I lined them up and decided whether they needed to be facing the front or rear.