You put your weeds in there, man!

Step one: Fill a garbage can lid with weeds from the garden. It should take less than a minute to fill the lid if your garden rows are niiiiice and weedy.

Step two: Deliver the lid to the Post Office Chickens in their "playpen." (Remember 4 weeks ago when they were itty bitty?) Spread the weeds around. Many chickens (the Reds, Welsummers, and Ameraucanas) will run away from you and your crazy lid, all the way to the opposite side of their yard. The friendliest chickens will stay around to see if this setup might be edible. What kind of chickens will do that? Mostly Orpingtons.

Step three: Allow the excited nasal piping of the weed-eating chickens to alert their peers that something is AWESOME. Observe as the aforementioned peers creep warily or flap excitedly over.
Step four: Inter-chicken weed tastings. Harmony and happiness.