Roast the bones and vegetables: Preheat your broiler. Arrange the turkey bones, onion, carrots, and celery on a baking sheet. Broil for approximately 20 minutes, or until the vegetables are slightly golden and some color has formed on the bones, indicating the release of natural sugars.
Simmer the broth: Transfer the roasted bones and vegetables to a large pot. Pour in the 8 cups of water, ensuring all ingredients are covered. Bring to a gentle simmer and cook for 2 hours.
Add aromatics (optional): If desired, add additional aromatics like fresh herbs (e.g., parsley, thyme) during the last 30 minutes of simmering. Do not add salt at this stage.
Strain and store: Carefully strain the broth through a fine-mesh sieve, discarding the solids. Let the broth cool completely before storing it in an airtight container in the refrigerator for up to 5 days, or freeze for longer storage.