The last parts arrived and I finally had some time. I soldered all the wires to all the boards. Six times 10 wires for the digits, six wires for the anodes and 2x2 wires for the two neon lights that act as a dot. Soldering everything together was a bit of a dirty job, I also lacked a few extra hands. But, it worked in the end.

After checking all wires for shorts, I felt condifent enough to put the boards in and test them.

Of course, I had the numbers mixed up, but that was easily fixed. And then, I had a working nixie clock!