Hello dear @lemouth, thanks to you for your important visit to my article, in relation to the system or set that I made with nails, after several attempts I got that the key to keep it together are the two nails that hold the system of particles, where, one is of less length and thickness than the other as seen below:

Now, my friend, I share with you the following images related to the structuring of this particle system but with other nails:

Another key (if necessary) is to rest one of our fingers on the shorter nail when lifting the system until the interlocking nails are held in place.

Sometimes the previous step is not necessary and this will depend on the shape of the head of the nails to be used, I hope these images have helped you to better clarify how I could keep in balance this system. Greetings and keep in touch.