First, place 2 pounds of bones in a pot of water and boil them for 15 minutes to remove the impurities. Then, bake bones on a foil-lined baking tray at 450 F. for 40-45 minutes.
Once bones are baked, slice 1 small/medium-sized onion and 1 head of garlic in half. Add bones, chopped onion, chopped garlic, 1 tbsp. salt and 1 tbsp. of apple cider vinegar to a 4 quart crock pot.
Add enough water to cover the bones, but leave a little space at the top for your broth to simmer. You don’t want it to over-flow as it heats and bubbles a bit. Simmer on LOW for 48 hours (If using the Instant Pot, set to Slow Cook and set to MEDIUM for 48 hours).
When your broth is done simmering, remove the bones and boiled vegetables.
Strain the broth through a mesh strainer to remove any other bits left behind.
Place broth in a refrigerator to cool for at least 4-5 hours. The layer of fat will harden on the top.
After the fat has hardened, remove the layer with a spoon. Discard the fat and use your broth to make a tasty soup!