Prep your veggies.
Add the chicken bones, veggies, peppercorns, and water to a large stock pot. Bring to a boil, then reduce the heat to medium low and simmer for 6 hours.
Strain the stock in a colander. Let cool and refrigerate overnight.
The next day, you will see that all of the fat has solidified on the top of the stock.
Skim the fat off the top with a spoon.
You are now left with clean stock that is congealed from all of the collagen in the bones.
Slightly heat up the stock until it uncongeals. Ladle the stock into ice cube trays and freeze.
Once the stock cubes are frozen, put in a gallon sized freezer bag and save for later use. 3 cubes = about 1/2 cup of stock.