I'm Using Walthers REA building as the basis for my North Shore freight house.
I just pulled the sprues out the box, started clipping and trimming to clean up the parts.
First wall up, getting it all square from the get go.
Second wall a-go-go.
Third wall in. I tried it out on the layout like this, but given the location was that I could see lack of the fourth wall. So I put that in to finish the basic build.