Make the broth. Place the bones in a large stockpot or roaster. Add the chicken feet, if using, along with the onion skins, celery heart and leaves, garlic cloves, and carrot tops.
Cover everything with water.
Bring the pot to a boil, then reduce the heat to a very low simmer. Cover and allow the broth to slowly simmer for 24 hours.
Check the broth occasionally and add enough water as needed to keep the bones covered.
After 24 hours, remove the bones and strain the broth thoroughly, removing the onion skins, celery, garlic, carrot tops, and all other solids.
Cool the strained broth and refrigerate until the excess fat rises and firms on the surface. Remove the excess fat.
Return the strained broth to a large pot and bring it back to a boil before filling your jars and proceeding with the pressure-canning instructions.