Combine all of the solid ingredients in a 6 quart Instant Pot.Pour in the filtered water up to the 4 liter mark.Seal according to manufacturer's instructions.Turn pot on and set to Manual / High Pressure / 60 minutes.Once time is up, cool and release the pressure according to mfg. instructions.Cool for one hour.Strain the solids out into a clean pot or large container.Season the broth with sea salt as desired.Chill for several hours or overnight.Remove the solidified fat from the top of the broth and discard.Portion into containers and store for up to a week in the fridge, or freeze for up to 3 months.You can add all of the ingredients to your slow cooker and cook on high for 8 hours - not sure you'll get exactly the same results with the bones getting soft, but you will extract enough from them to make a delicious and healthy broth!