Strip off all the usable meat from the carcass & refrigerate.
Separate wings, thighs, and legs from the carcass and use kitchen shears to cut the carcass into smaller pieces. Layer the bones in a large roasting pan.
Add the veggies and garlic to the roasting pan. Roast together until the bones are brown, about 40 minutes. Stir halfway along for even browning.
Transfer the bones and vegetables to a large pot. Add 1 cup of water to the roasting pan. As the water steams, scrape the pan with a wooden spoon to release the flavor infused brown bits stuck to the bottom of the pan. Add to your stockpot.
Add the spices and enough water to cover the bones by a couple of inches. Turn the heat to medium-high & bring to a boil. Reduce the heat and simmer at least 2-3 hours. Stir occasionally and skim off any foam.
Remove the larger bones from the stock and strain the liquid through a fine mesh sieve into a large container. Discard the bones and solids. Let the stock cool completely, then refrigerate. Once the stock cools in the refrigerator, the fat will rise to the top. Skim off the fat.
Set aside 4 cups and freeze the rest.