>>2938767
Once hardened, simply cut the mesh with scissors and you have your tower. You also have to ask yourself where you want to put it at this point.
Now that the tower is done, we'll have to add a way to water it conveniently, and to do that, we'll have to drill our last two holes. One in the tower, one in the container. As for the size of this hole, bigger makes watering easier, but also increases the chance of spores, dirt and animals getting in there, so I'm a fan of smaller overall.
I'll use cheap plastic pipettes to refill the tower, and those have a 3mm end, but I chose a 5.5mm drillbit. Truthfully you can get away with larger if you want an easier time watering.
You can also drill this hole at the end, after the grout has dried, if you choose not to use plastic straws. It'll lead to a bit more water seeping into the grout, which may or may not be beneficial depending on the ant variety. It will more importantly be easier to drill though, so frankly, I think making that channel at the end and skipping the straw might be the way to go rather than how I did it here.
Anyways I drilled the hole into the water tower and container, and cut a piece of the plastic straw to size and glued it onto the tower with hotglue (but any glue should work).