Preheat your oven to 425 degrees f.
Place your meaty bones in a large roasting pan and season generously with sea salt and pepper. Roast in your preheated oven for 30 minutes.
Once the time is up, flip the roasted bones over and then add all of your chopped veggies and garlic to the roasting pan.
Return to your preheated oven and roast for another 30 minutes.
Carefully transfer the bones and veggies to a large 6 quart (or larger) stock pot. Add the thyme, bay leaves, and parmesan rind, then fill it with water until everything is submerged. It will fit about 4 quarts of water give or take. Adjust to your pot.
Bring to a boil over HIGH heat, then reduce the heat to LOW and simmer, covered tightly for at least 6 hours. You may simmer your broth longer if desired up to 24 hours or so. You'll need to keep a good eye on it so that it's constantly covered with some water or you'll burn your broth (and possibly create a fire hazard). Plan to check on it once every hour or so to be safe, and add a bit more water as needed.
Allow your broth to cool until it's safe to handle, then strain and discard the solids.
After cooking you'll be left with a little over 3 quarts, or about 15 cups of broth.
Cool completely then refrigerate until all the fat has set on top; skim the fat and discard.
Keep refrigerated for up to 4-5 days or freeze in 1-cup batches for up to 3 months.
Enjoy!