Place chicken bones, onions, and carrots into a large stock pot.

Add water to the pot, filling it at least three-quarters full.

Add vinegar to the pot.

Let the mixture sit for 1 hour.

Bring the mixture to a boil, then skim off any foam or impurities that rise to the surface.

Reduce heat to a simmer and cook for at least 8 hours, or overnight.

Let the stock cool enough to handle.

Strain the stock through a strainer, discarding the solids (bones, vegetables).

Pour the strained stock into mason jars, leaving 1 inch of headroom.

Let the jars cool to room temperature, then transfer to the freezer.

Pick meat off the chicken and use for other recipes.