3–4 pounds of mixed grass-fed beef bones (marrow bones, oxtail, knuckles, short rib, etc.)
2 medium onions, chopped
2 medium carrots, chopped
3 celery stalks, chopped
2 bay leaves
2 tablespoons apple cider vinegar
1 tablespoon peppercorns
8–10 cups water (or enough to cover ingredients)
Heat oven to 400°F.
Place the mixed bones in a roasting pan in a single layer and place it into the oven. Roast the bones for 30 minutes. Turn bones over and roast another 30 minutes.
While the bones are roasting, chop the onions, carrots, and celery. You are going to discard these after long hours of cooking, so a rough chop works great!
Place roasted bones, chopped vegetables, bay leaves, apple cider vinegar and peppercorns in a 6-quart crockpot. Cover completely with water.
Cover and cook on low for 24 hours. Add water as needed to keep all the ingredients covered in water and periodically skim the foam off the top of the pot.
After 24 hours, the broth should be a dark brown color. Discard all solids and strain the broth through a fine mesh strainer into a large bowl. Strain once more through cheesecloth to remove any remaining particles if desired.
Ladle the bone broth into Mason jars and let it chill to room temperature. Bone broth can be stored in the fridge for up to two weeks or frozen for future use. Before using, skim off the accumulated fat on the surface.