Bring carcass and skin, broth, any or all optional extras, and 4 cups water just to a boil in a stockpot or large Dutch oven over high heat. Reduce heat to low, and simmer 2 to 3 hours or until carcass falls apart and stock tastes like chicken soup. Add water to cover if bones become exposed.
Remove and discard large bones. Pour liquid through a fine wire-mesh strainer; discard solids. Cool completely (about 1 hour).
Pour into portion-size containers or zip-top plastic freezer bags. Refrigerate up to 1 week or freeze up to 6 months.
We tested with Swanson Natural Goodness 33% Less Sodium Chicken Broth.