- Preheat over to 450°F. Place beef bones, carrots, leek, onion, and garlic on a roasting pan or rimmed baking sheet and roast for 40 minutes, stirring halfway. 
- Fill a large slow cooker with 12 cups of filtered water. 
- Next, add celery, bay leaves, peppercorns, and vinegar to the pot of filtered water. 
- Add the roasted bones and vegetables into the pot along with any juices. 
- Add additional water as needed to cover bones and vegetables. 
- Cook the bone broth on low for 8 - 24 hours (the longer the better). 
- Let the bone broth cool slightly and strain the bones and vegetables. 
- Refrigerate in airtight mason jars until fat is solidified on the top of the broth. 
- When ready to use, scrape excess fat and warm the broth on low heat until it is liquid consistency. 
- Add sea salt and fresh herbs to taste.