In a large stockpot, place the turkey carcass, onions, carrots, celery, garlic, peppercorns, bay leaves, parsley, sage, and thyme. Fill the pot with enough water to cover all the ingredients.

Bring the pot to a boil over high heat, then reduce the heat to low and let it simmer gently for about 2-4 hours. Skim off any foam that forms on the surface.

After cooking, add salt if using. Then, remove the pot from heat. Strain the stock through a fine mesh sieve into a large bowl or another pot to remove solids.

Allow the stock to cool, then transfer it to storage containers. Refrigerate or freeze as needed.