Found this today when searching the really old pictures on my pc.
I had concrete back then, because we used it for some study projects, this kind hardened fast. Th usual one that needs days to harden could also be used, but I never was good at waiting.
some material to build a mold
the fast hardening concrete
something to mix in
We build our form, I used foam and decided I would make the standard four edged socket.
We pour a little bit of the plaster into every mold (it is good to have more molds).
Why we don't pour everything into one?
Concrete develops marking lines, where the first layer dried and every layer adds a new one.
Here is an example from some other project:
Then we just add as many layers as we wish until our form is filled.
After dried, you can just unmold them.
Those sockets are great for urban projects!
You can vary the surface by using different materials for your mold. Just play!