Preheat oven to 230 C / 450 F.

Place the chicken carcasses and any bones you have into an oven tray.  Lightly drizzle with olive oil and generously sprinkle with sea salt.  Roast in the oven for 45 min – 1 hour or until golden brown.  Be careful not to burn them.

In a large stockpot, add onion, garlic, carrot, celery, rosemary, thyme and roasted chicken pieces along with any roasting juices in the oven tray.

If you have any brown bits stuck to the bottom of the baking tray, add a cup or so of hot boiling water to the pan.  Let sit for 20 minutes or so until softened up then stir up the pan.  You should get a nice, golden brown liquid from this which you can add to the stockpot.  This will provide a richer flavor and darker color.

Fill stockpot up with water and heat on the stove on high heat until you reach a boil.  Once a rolling boil has been reached, reduce heat to low, cover and let simmer for 3-4 hours.  After 3-4 hours, the carcasses should be broken down and all the veg material will be mushy.

Place a colander over a large bowl or stockpot and strain stock through a colander.  Discard debris and season remaining stock with sea salt.  It should take 1-2 tsp of sea salt depending on personal taste.

Let cool then package up in the freezer for future use.