Combine all except for the salt in a large stockpot or kettle.
Bring the water to a rolling boil over high heat.
Once boiling, reduce the heat to low and let the broth simmer gently, uncovered, for 3 to 4 hours. The longer it simmers, the more flavor will be extracted from the vegetables.
Carefully strain the broth through a fine-mesh sieve or a colander lined with cheesecloth into a large bowl or another pot.
Discard the solids.
Taste the strained broth. If the flavor seems weak, return it to the pot and continue to simmer, allowing it to reduce and concentrate the flavor to your liking.
Season your finished broth with salt to taste. Use immediately, or let it cool completely before storing in the refrigerator for up to 3 days or freezing for later use.
Freeze cooled broth in ice cube trays for small, convenient portions perfect for deglazing a pan or thinning a sauce.
Once frozen, transfer the cubes to a freezer bag.