Preheat your oven to 450 degrees F. Place bones and veg (carrots, onions, garlic, celery) to the roasting pans. They should only be in a single layer. Use two pans if necessary.
Roast for about 30 minutes before gently tossing the bones and vegetables, and roasting for an additional 15-30 minutes more.
Transfer bones and vegetables to your stockpot. Also scrape up any remaining bits and juices remaining in the roasting pan using a metal spatula and a little water, if needed, and add to your stock pot.
Fill your pot with approximately 12 cups water, or until bones are fully submerged. Bring the bones to a rolling boil. Add the bay leaves, peppercorns, star anise, parsley, and cinnamon sticks to the stock pot. Cover the pot and reduce heat, bringing it down to a simmer. Skim any foam or excess fat off the top, when you notice it forming. Simmer for 3-4 hours.
Strain broth through colander and chill. (You may use the first broth for soups, stews, or sipping.) When cool enough to handle, transfer bones and veg into a large crock-pot, removing meat scraps and setting aside. Add 1 Tb apple cider vinegar. Cover with water again, and cook on "low" for at least 24 hours.
Strain a second time, discarding all veg and bones (our chooks love the worn out veg; the doggies adore the bones). Chill, and remove fat from the top.
Taste and add salt and pepper, to taste.
Refrigerate and use within 4-5 days, or freeze for up to 6 months.