Originally Posted by
bjoerges
Bicycles are typically assembled by the LBS. Typically they arrive in a box about 56-66" long, 24-36" tall, and 12" wide (very rough estimates). Depending on the bike, the brakes, rear wheel, cassette, chain, chainrings, and crank are assembled. The front fork is in the head tube but not attached to the handlebars or front wheel. The front wheel sits alongside the bike and is zip-tied to the frame. The handlebars dangle by the brake and derailleur cables or are also zip-tied to the frame.
Zip ties are cut and the assembly begins! After finishing, the brakes and derailleurs need adjusted.
(LBS employee)
And depending on the LBS. They either fast forward the assemblies, e.g just put it together or do the complete thing like normalizing the tension on wheels + adjusting everything that could be adjusted.
Bad shops do the former, better shops do the latter even though it costs more. So to answer the OP's question. You can do an assemblin in < 15min if you do a **** one. About an hour for low end bikes with loose ball hubs/headsets etc.