These are the FischerTechnik parts you need to build the clock, except for the switches that are used to detect that he hands are in the 12 o'clock position. I used my Hobby1, Hobby2 and Computing (1987) boxes. You don't need the (black) base plate shown in the background, that's just a box I used for better contrast in the pictures. The electronics to turn motors on and off and keep track of time aren't part of the build instructions, they are covered by the Project Logs.

The first part of the main frame.

More main frame, and the 10-tooth gear that drives 10:40 reduction for the hour hand.

This helper gear is part of the 10:40 reduction for the hour hand, basically it helps to adjust the spaces between the gears so the minute hand and hour hand can be on the same axle.

Disk with hour hand and 40-tooth gear. I forgot to take a picture that shows that the hub in the 40-tooth gear is flat on the back side. The hub should not be tightened!

There's nothing to mount this on yet, put it aside for "a minute" (see what I did there).

Minute hand.

Mount minute and hour hand onto the frame. Note: the hour hand should be able to rotate freely around the axle. Do not tighten the hub on the hour hand!

10:30 reduction for the minute-hour mechanism

We will add another helper gear between these gears in the next step.

Helper gear for 10:30 reduction and second part of the frame

After this, you should see that there's a 12:1 reduction between the minute and hour hands: rotate the minute hand 12 times and you'll see the hour hand go around exactly once.

40-tooth gear driving the minute axle