Heat the oven to 425 degrees.

Layer the bones on a parchment lined baking sheet.

Roast the bones for 20 minutes.

Place the bones into the bottom of the Crockpot.

Pour the apple cider vinegar and salt if using into the Crockpot.

Add in 8 cups of water to just cover the bones.

Cook on low for 12 hours.

Let cool and skim off the fat from the top before storing or serving.