Combine everything in a large stock pot. Cover with water until the solids are submerged by 2-3 inches of water when pressed down (they will naturally float).
Place the pot on the stove over high heat. When small bubbles begin to break the surface, reduce the heat to medium-low, and place your colander insert, steamer basket, or drop lid inside the pot, if using. (See recipe notes in article above for more information.)
During the first hour of simmering, use a skimmer or spoon to skim any skim that rises to the surface of the stock and discard.
Keep the pot at a low simmer (so that just a few small bubbles rise to the surface continuously) for 5-6 hours. Add water as needed to keep the colander insert and solids covered by 2-3 inches of water when pressed down.
After 5-6 hours, remove the stock from the heat and remove the colander insert or perforated drop lid. At this point you may choose to allow the stock to cool for 30-60 minutes.
To strain, line a large bowl or pot with a flour sack towel or cheesecloth if using. Place a colander on top of that and pour the stock through. Pause to discard solids into a paper grocery bag as needed.
Remove the colander, then pick up the corners of the flour sack towel or cheese cloth and let the stock strain through. Now straining is complete.
Allow the stock to cool to room temperature, then ladle into containers and store. Stock will keep in the refrigerator for 5-7 days, or in the freezer for 1 year.