Set the oven to 400°F/200°C. Place the chicken bones, chicken leg, carrots and onions on a tray and in the oven for about 1 hour or until dark brown but not burnt.
Once roasted, add to the instant pot. Add a bit of water to the roasting tray and try to remove all those delicious brown bits from the tray. Add this to the Instant Pot.
Add the rest of the ingredients and cover the bones with cold water to the max line of the Instant Pot.
Set sauté function for 20 minutes and wait for the stock to boil. Once boiled, turn off the sauté function and skim the foam from the top.
Close the lid and set the Instant Pot to 45 minutes on high pressure.
Leave the Instant Pot to natural release the pressure for about 15 minutes. Manually release the rest.
Skim off any fat from the top and strain the stock through a fine mesh strainer.
Cool the stock in a bath of ice and refrigerate.