Place the chicken bones and skin in a large stockpot.
Add the quartered onion, carrot segments, celery rib, and fresh parsley to the pot.
Fill the pot with enough water to cover the ingredients by 2 inches.
Stir in the salt and black pepper.
Bring the mixture to a gentle boil over medium-high heat.
Reduce the heat to low and simmer, uncovered, for 6 hours. Skim off any foam or fat that rises to the surface.
Strain the stock through a fine-mesh sieve into a large bowl, discarding the solids.
Allow the stock to cool completely before transferring it to storage containers.
Refrigerate for up to 3 days or freeze for up to 6 months.