Preheat your oven to 400 degrees

Place the bones, carrots, celery and onion in a large, oven safe soup pot

Sprinkle with salt and pepper

Place uncovered in the oven for 15 minutes (this roasts the ingredients slightly and gives a little more depth of flavor to the broth, but it's not necessary)

Remove from the oven and fill the pot with filtered water until all ingredients are submerged (I go about a 1/2 inch above the ingredients)

Add 2 tablespoons apple cider vinegar if you have it (supposedly this helps draw the nutrients out of the bones - I've done it both with and without)

Bring to a boil on the stovetop and reduce to a simmer

Simmer for 8-24 hours, skimming the scum off the top as it rises

After your desired simmering time, let the broth cool to room temperature

Drain the broth and discard the bones and veggies (I usually just drain into a smaller stock pot)

Place in the fridge overnight

The next day, skim the fat layer from the top of the broth

Add the juice of 1/2 lemon and salt and pepper to taste

Store in an airtight container in the fridge for five days or the freezer for 3 months