Preheat the oven to 425°F.
Place your bones spread out on a large parchment lined sheet tray. Place in the oven and roast for 45 minutes to 1 hour, or until they are golden brown.
Transfer the bones to a large stock pot and cover with 2 inches of cold water. Place the pot on the stove and bring it up to a very low simmer. Simmer on low, with a lid, for 8-12 hours.
In the last hour of cooking, add the onion, carrot, celery, bay leaves, thyme and garlic. Simmer for one more hour then turn off the heat.
Discard the bones and then strain the broth through a fine mesh strainer over a large bowl. Distribute into storage containers and keep in the fridge for up to 5 days, or freeze.
