Start with cold water. You don’t have to wait for the water to start boiling to add the vegetables. Put everything into a large pot, turn the heat on to high and wait for it to start boiling. Once it starts boiling, reduce the heat to medium-low and continue boiling for two hours uncovered.
Strain the broth through a fine mesh strainer and store the broth in airtight containers or plastic ziplock bags.
Broth will be good for 3-4 days if stored in the refrigerator, or 4-6 months if stored properly in the freezer.
For a more concentrated broth, reduce the amount of water to 5 quarts.