In a large stock or pasta pot, add the turkey carcass and vegetables and cover with water. Bring it to a simmer.
When froth forms, skim and remove it with a large spoon, then add salt and peppercorns. Continue simmering for 2 to 3 hours. The liquid will reduce slightly.
Carefully strain the hot liquid through a sieve, being sure to press the vegetables and bones with the back of a wooden spoon to extract the flavor.
Divide the liquid into several containers and place them in the refrigerator to cool. They will last several days in the fridge or freeze them, as we like to do, for future use.