Prep. Cut the vegetables into large chunks. You can leave the garlic cloves whole, just peeled. Rinse the bones well to remove any blood or other impurities.

Sear the bones. Set the Instant Pot to Saute (Normal setting) and once hot, add a little oil. Sear the beef bones (in batches if needed) for 1-2 minutes on each side and then on the edges as well. Remove to a plate and press Cancel to stop the Saute function. 

Deglaze. While still hot, pour in a cup of water to deglaze the pot. Use a spatula to scrape off the bits of meat or fat stuck to the bottom, which will remain in the liquid.

Add all ingredients. Add the bones back to the pot and lay the vegetables around. Add the garlic, peppercorns, bay leaves and half a teaspoon of salt. Pour in 5 more cups of water (total of 6 cups, about 1.5 litres). You can add a little more water if you want. 

Pressure cooker. Select the Soup/Broth button and press it a couple of times to cycle through setting options until it says MORE and the time shows 4 hours on HIGH. You can also do this manually by selecting Pressure Cooker, HIGH pressure and adjusting the time to 4 hours but it can be a little tedious to change the time.

NPR. Once the time is done, allow the pressure to release naturally. Total time including pressure build-up and release should be about 4.5-5 hours. 

Strain & store. Remove the bones and strain the stock into a large bowl or a separate pot. Pour into clean glass jars or Tupperware containers and cool down before refrigerating or freezing.