I like to put my cells in a brood frame, as close to the top as possible, but still withing the brood, not into the honey cap. The few capped brood cells that I will destroy with the queen cells wont be missed. When I am placing cells into spring splits, this year nearly 700 cells in less than 12 hours, i dont have time to search for a spot where i wont destroy brood. So the go onto a brood frame, as close to the center of the hive as possible, and as close to the top of the frame, while remaining in brood.