Preheat oven to 400 degrees F/ 200 degrees C.
Place beef bones on a lined baking tray. Brush beef bones, both sides with olive oil and roast for 1 hour.
Place your carrots, celery, onions, roasted beef bones, water to cover beef bones and apple cider into your crock pot.
Place crock pot on low heat and slowly simmer for at least 12-48 hours to let the flavors develop.
Once the broth is finished cooking remove the beef bones and vegetables and strain the broth through a strainer lined with either cheesecloth (or medical gauze bandage if you cannot find cheesecloth)
Allow your nourishing slow simmered beef bone broth to cool. Place beef bone broth in glass container but leave room at the top if you plan to freeze them later (glass will break in freezer if the liquid does not have room to expand when frozen).
Place in the refrigerator. The broth will turn into a beef broth gelatin-jello and the fat will solidify on top.
Skim fat off top of beef bone broth with spoon.
Heat your beef broth gently on top of the stove and enjoy either in a mug with a little salt or use in your favorite soups and other recipes!
Beef bone broth can be stored in the refrigerator for up to 3 days or can be frozen for up to 3 months.