5.5L Slow Cooker Instructions:

2 kilos of chicken feet
4 tablespoons of Apple Cider Vinegar
Cover bones with water
Cook on low in slow cooker for 24 hours (do outside if you don't want to be stunk out!)
Remove bones
Pour into containers
Keep in the fridge what you will use in a week and freeze the rest
When set, scrape fat off the top

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2023 update: After many years of making this, I just wanted to let you know, you can put more water in that just an inch above the bones, take your water to the top fill line of the slow cooker bowl, that is perfectly fine :)

Also, if you wish not to waste the bones, get your hand stick mixer and blend them down to a fine paste that looks like mousse. This will set like mousse in the fridge. Putting them in molds/moulds is also a great way of storing them so you can pop a mold/mould in your dogs bowl from time to time. Keep in the fridge what you would use within a week and freeze the remainder.

If you wish to use a pressure cooker, you'll do exactly the same, except, you'll only cook for 2 hours.

You can use beef joint bones too, but you'll need to slow cook for 36 hours or pressure cook for 4 hours.