eg:
you have 10 frames in the brood chamber
you take one out, and cut half of it out
because bees are in such need of drones (assuming you are using ordinary foundation) they will 100% fill that half with drone cells and queen is going to lay inside them.
when drone larvae developes mites infest the cells, mites are drawn to drone brood up to 10 times as to worker brood, that's why drone brood is bound to get high number of mites, after the drone brood is capped-the mites are trapped in, you cut it out and...feed it to chickens, or something..