We are keeping our bees in Zander frames. We just take a frame without middlewall and without wires and they make only drones in this. We cut that out and freeze it to kill the drones in the most gentle way. If you open the cells you can see the varroa sitting on the drones, they prefer drone cells because they are bigger.
Discussion
Those varroa will be born on the bees, you are correct. We have seen larvae with a varroa already in place, just waiting for that bee to be born. The varroa is such a parasitic vampire. I detest them!