for start , some translations from slovak to english (I am lazy to make different pics)
Korok = cork
sadra = plaster
sadrovy odliatok = plaster form
I am not sure if anyone tried this before , but I´ve never seen it. I just tried it first time today and it looks really fine

All begun by this tube upgrade:

I wanted to make chambers inside by cork pieces (circle) , but it was really hard to make. So I put inside pieces of cork ... vertically/horizontally/vertically/horizontally.... etc. until enter. From top of tube it looked like "X" .
I used small acryllic box (20x20x20cm cube) and I put there 5mm of plaster. I put there tube , and plaster came in - until horizontal cork pieces. So if you watch on tube , there are chambers with cork ground and with plaster ground

Idea is about better ground for brood of ants. We all know that clean glass is not sometimes good for evolving of larvae/eggs , so this is maybe solution. I am going to test it , I will put there some Lasius colony or so - maybe later Myrmica because their brood is in tube difficult to evolve on glass.
When plaster was fresh , I put on it some soil and small stones as decoration. I´ve also built enter to nest and put there a piece of green died moss.
Now is all wet , but when it will a bit dry , I will try to put water on ground in arena -> plaster on ground will suck it probably and make wet also plaster inside tube = fine fresh wet ground for brood

Pics:




Enjoy