Heat vegetable oil in a large soup pot and add chopped onion, 2 stalks celery, and garlic. Cook gently until tender and fragrant, about 5-10 minutes.

Add the turkey carcass, chicken broth, tomato sauce, and enough water to cover. Include garlic salt, pepper, and fresh herbs. Bring to a boil, then reduce to a simmer and cook for 1 hour, skimming foam as needed.

Strain the broth into another pot. Discard solids. Once cool enough, pick all meat from the carcass and return to the broth. Add the remaining 3 stalks of chopped celery and any additional leftover turkey.

Simmer for 90 minutes, adding the carrots about 45 minutes before serving. Serve the soup ladled over fine egg noodles.