Place your tame hens at the top (in reality you place the eggs there and hatch them using a brasier etc), feed them seed by throwing seeds in front of them (feed from containers is highly suggested).

Since eggs are dropped down the chute (they don't break), the hens will keep breeding as long as they are fed.

Another version of this (just build 2 of them) is to place firepits or brasiers (I like hanging braziers) at the one tower to hatch the eggs that are produced for an automated Eggs -> Chick -> Chicken breeder

Hens are protected and fairly save from bat raids etc