Pre-heat the oven to 375°F.
Pull the leftover chicken off the roasted chicken bones and shred into bite-size pieces; set aside to add at the end.
Lay the bones and skin, from two roasted chickens, on a baking sheet; place in the pre-heated oven; roast until brown; about 45 minutes.
Remove from the oven and add the roasted bones to a dutch oven or covered roasting pan; cover with 10 cups of water, chicken stock or a combination of both.
Add a celery stalk, 3 cloves crushed garlic and a roughly chopped onion to the pot.
Reduce oven to 325°F; place the covered pot or roasting pan in the oven and roast for 2 hours.
Remove from the oven and let the stock sit and cool to room temperature before straining it through a colander or sieve; place in an airtight contanier; place in the refrigerator and chill for a couple of hours or overnight.
When it solidifies at the top, remove from the refrigerator; this should produce about 8 cups of stock.
