I have wire fronts screwed on the boxes, with doors that can be put on if needed. They very seldom are.
They are different colours, more to please me

and they are staggered left and right in each row. I hardly ever have a bird in the wrong box, broken eggs, that sort of thing.
Works for me.
Greetings from the land down under.

Blessed is he who expecteth nothing, for verily, he shall not be disappointed.