The way it was demonstrated by my teacher was something like the following. Note that I have not done this myself, but have seen it demonstrated multiple times.
1) Take a large piece of aluminum wire, 3.5mm+, depending on the size of the drainage hole. The length should be enough to wrap from the drainage hole to the upper rim of the pot, with at least 12cm extra length.
2) Jam the wire into the drainage hole, a few cm is fine, doesn't need to be too deep
3) make a tight right angle towards the edge of the pot, then another bend over the edge, to vertical. This will put the upward force of the guy wire onto the bottom surface of the pot, keeping it anchored.
4) Make a loop with a few twists of wire, then anchor your copper guy wires to that loop. My teacher was putting 5 or more wires on a loop with no problem.
I wish I had pictures or videos, because it's really intuitive when you see it.