Place the beef bones, carrots, onion, celery, garlic, apple cider vinegar and sea salt in a slow cooker.
Cover with water, filling the slow cooker up to about 1 inch from the top.
Cover and cook on low for 18 to 24 hours.
Strain the broth through cheesecloth or a colander and cool. When the broth cools, there will be a layer of fat on the top, which can be removed and used for cooking. Use the broth as a beverage (reheating it, of course) or as a base for recipes.
Recipe by Easy Health Options® at https://easyhealthoptions.com/?p=72153