An acquaintance of mine dabbled in chicken farming as a summer side business. It turns out that raising "cage free" chickens is a fairly easy thing to do. You buy the chicks in the spring and put them out in the yard, inside a wire mesh house. The house has an open bottom, and you move it every day so the chick(en)s have fresh grass. Half of the house is covered with fabric to provide shade. The main purpose of the enclosure is to keep out predators and maintain flock coherence; there will inevitably be escapees, but rather than running for the hills they just wander around and eventually get lost or eaten if you don't bring them back in. Domestic chickens are observably very stupid. But of course you're not here to learn about raising chickens, you're here to learn about the peri- and postmortem excitement!
If you're a part-time chickenisto, when harvest/slaughter time comes you go and get the kill cart. This is a special trailer designed for the efficient killing and processing of chickens, collectively owned and time-shared by the local chicken farmers. An entrepreneur need only buy in to the group and, on their appointed day, fetch the cart from the last user. This system makes it easy to enter the business without a significant investment of time and money.
The kill cart is all stainless steel. Every surface is either full of holes or sloped toward a particular drain, keeping fluids out of the way and allowing the whole to be conveniently hosed down for cleanup. There are particular stations around the perimeter of the trailer for different parts of the process, some of which are connected to the large propane tank mounted just aft of the hitch.
Chickens enter at the front of the cart, several at a time. They are placed into "kill cones", metal funnels which hold inverted chickens with their heads poking out the bottom. These prevent the victims from flailing about and damaging themselves, and position them for convenient slaying and draining. It is important to note that the chicken's heart keeps going even after it is arguably dead, getting the blood out quicker. (This is the first problem with industrially processed chickens. They are typically electrocuted, instantly stopping the heart and leaving more blood in the body for the later stages.)
Dead, bloodless chickens are removed from the cones and passed to the plucker, who removes some larger feathers before putting the corpses in a convenient cleaning device. This is somewhat like a washing machine, having a rotating drum with thick rubber prongs on the walls. Hot water cleans the chickens and loosens the feathers, which are then stripped off by the prongs.
The naked, pink, dead, bloodless chickens are put on the evisceration table, where a couple more technicians perform Step Four, as described above by mrklaw. The table is ergonomically designed and directs unwanted guts into easily emptied catches, while channeling fluids out the bottom to the ground. At the end of the table, also the end of the trailer, is the first of two dedicated quality control workers. Their job is to make sure that all guts have been removed, and especially that no feces has been spilled during the evisceration. (This is the second problem with factory chickens. Bulk processing requires mechanical evisceration, which is indelicate and likely to rupture guts and intenstines. Individual hand-treatment greatly reduces the risk of infectious contamination.)
Moving back up the other side now, the naked, pink, dead, bloodless, gutless chickens are tidied up through removal of feet, necks, and other unwanted protrusions. They are then plunged into an icy water bath, under the supervision of the second quality controller. This is the terminus of the process, the output queue of the kill cart. At the end of the day the prepared chickens will be transferred to a larger basin of ice-water, from which customers can choose their own.
The comprehensive facilities of the kill cart and the (dis)assembly line division of labor enable approximately seven people (three would be a skeleton crew, and with ten the cart would be pretty crowded) to slaughter the whole flock of 50-100 in one fun-filled afternoon. Cleaning up is relatively easy too, no harder than washing a car. This gives "killing day" a kind of party atmosphere; you invite a few friends over, you slaughter the chickens, you have some beer, you sit around in the evening and talk about what you're going to do with the money. And few things taste better than an all-natural grain-fed chicken you assisted through its entire life cycle!