In a large stockpot, add the turkey carcass, carrots, celery, onion, garlic, bay leaf, thyme sprigs, fresh parsley, kosher salt, and pepper. Cover with 16 cups of water. Bring to a boil, reduce to a gentle simmer, and cook 3–4 hours until reduced by half (8 cups), occasionally skimming foam from the surface. Strain the broth through a fine mesh strainer and set aside.
1 Cooked Turkey carcass, 3 ribs Celery, 3 medium Carrots, 3 cloves Garlic, 1 large Sweet onion, 2 Bay leaves, 5 sprigs Fresh thyme, 5 sprigs Fresh parsley, 1/2 tsp Kosher salt, 2 tsp Black pepper corns, 16 cups Water