Start with cold water: Place chicken (roasted or raw) in a stockpot. Add cold water to submerge completely (about 1 quart per pound of chicken).
Bring to a gentle boil: Over medium heat, bring to a boil. Skim foam from the surface for a clearer broth.
Add vegetables and herbs: Lower heat to a simmer. Add celery, carrots, onion, garlic, herbs, peppercorns, bay leaves, and any optional ingredients like ginger or tomato.
Simmer low and slow: Simmer uncovered for 2–4 hours.
Strain the broth: Strain through a fine-mesh sieve or cheesecloth into a clean container. Discard solids. Cool completely before storing.