Fill the crock pot with filtered water until bones are just covered.
Add apple cider vinegar, cover, and let sit for one hour.
After an hour has passed, turn the crock pot on low and let it cook for 10-12 hours.
Remove bones and vegetables from crock pot, and strain broth using a fine mesh strainer, cheesecloth, or coffee filter.
Transfer the broth to fridge to cool. Once cooled, the fat will have risen to the top - you can either discard or save it to use as a cooking fat. Store broth in fridge up to 3 days, or in the freezer up to one year.
To make a second batch of broth from the same bones, simply return the bones to the crock pot, fill it with more water, and let it cook again. After the second batch, the bones should be brittle enough to crush easily between your thumb and forefinger.
When finished, discard/compost bones and vegetables.
Recipe by Nature's Nurture | https://naturesnurtureblog.com/homemade-bone-broth/