Here's a time-lapse photo of the assembly of a Saturn V S-IC (first) stage in the Michoud Assembly Facility Vertical Assembly Building.

At left is the thrust structure. Next, the fuel tank has been lowered into position. The next two pictures show the intertank structure and the LOX tank being installed, with the picture at far right being the completed stage.

I first saw this picture on eBay many years ago. I didn't buy at the time, but then later regretted it. I searched the Internet and bugged the helpful and friendly folks at Marshall's MIX, but was unable to find anything other than low-resolution versions of this on the Internet. Years later an eBay auction for a vintage Michoud Assembly Facility press kit, containing an 8x10 of this photo, came up and I am now the proud owner of a print of this photo!

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NASA photo 12898-1.
Scan by heroicrelics.

Here's a scan of the back of the picture:

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NASA photo 12898-1.
Scan by heroicrelics.

It reads

NEW ORLEANS, La. - This sequence of photographs, taken over a three-month period, shows vertical assembly of the Saturn V first stage at the National Aeronautics and Space Administration's Michoud Assembly Facility here. Built by The Boeing Company Launch Systems Branch, the booster measures 138 feet tall and 33 feet in diameter. The five major structures of the 7.5-million-pound-thrust first stage are assembled in Michoud's Vertical Assembly Building. The thrust structure, which supports the rocket's weight and distributes the force of the engines upward, is the first major component moved into the assembly tower. The fuel tank, with a capacity of 210,000 gallons, is positioned above the thrust structure. The intertank, a corrugated shell, is then lowered into position where it connects the fuel and liquid oxygen tanks. After the 330,000-gallon-capacity liquid oxygen tank is placed on the intertank, the booster is topped off by a forward skirt, onto which the Saturn V second stage will be attached. The three-stage Saturn V will launch manned flights to the moon within this decade.

# # #

And, years later while rummaging through the archives the University of Alabama at Huntsville, I ran across the following diagram which explains the assembly process in greater detail (albeit lesser visual appeal):

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From page 7-303 of Saturn V Booster Stage S-IC Manufacturing Plan Volume 2. Located in the Saturn V Collection, Dept. of Archives/Special Collections, M. Louis Salmon Library, University of Alabama in Huntsville, which also makes this document available as a 22.5 megabyte PDF.
Scan by heroicrelics.

So, to build your own S-IC stage, simply perform the following steps:

1. Position thrust structure assembly in tower.
2. Position & join fuel tank assy to thrust structure assembly
3. Position & join intertank structure to fuel tank assembly
4. Position & join oxidizer tank assy to intertank structure assembly
5. Position & join forward skirt assembly to oxidizer tank assembly
6. Completed vertical final assembly

Et voilà!