Warning: Although I've cooked the following low-temperature chicken two or three times without a problem, I'm no longer convinced that it is safe (see this question). Nevertheless, it is advocated by a well-known and respected chef, so I won't delete this answer unless I'm able to establish to my own satisfaction that it is, in fact, unsafe.
According to this article, also backed up with data from the USDA, you can cook chicken as low as 140F (60C) as long as the internal temperature of the bird reaches and maintains that temperature for at least 35 minutes.
You may have to do a little calculation and experimentation to find a chicken weight and temperature that hits the five hour mark, but it seems that you can do it safely as long as you have,
- an oven that can maintain a
temperature (I would invest in an
oven thermometer to be sure, most
oven dials are way out);
- a good
digital probe. Probe the meat in
several places to make sure of the
I would also leave the meat to rest a while so that cooking continues with the residual heat. I don't know how long you would need to feel safe, but I would probably wait 30 mins.
A tip taken from a Heston Blumenthal recipe is to brine the bird before hand. That way you will also kill a lot of bacteria from the skin.
Brining won't kill bacteria. The Blumenthal recipe involves dunking the chicken (see In Search of Perfection p.56) twice for thirty seconds in boiling water. I imagined, erroneously as it turns out, that this was a regular part of the brining process.