Roast bones 30 minutes at 400-450 degrees. Place bones in large stock pot, add apple cider vinegar and cold water to cover the bones, allow to rest for 30 minutes. Add more water (I’ve done up to 8 or 9 quarts, but you can experiment with how flavorful you want it to be. Sometimes it’s easier to store a more concentrated broth, and then add water when cooking with it). Bring to a simmer on high heat, skimming broth the first hour. Cover and simmer on low for 12 hours. Add carrot, onion, garlic, and celery and simmer another 12 hours.Strain broth and keep in glass jars. You can even freeze (just don’t fill jars up past the shoulder, and don’t screw the lid on all the way until they’re frozen solid).