Heat enough chicken fat or neutral oil to coat the bottom of a pressure cooker or InstaPot to medium-high.
Slice half an onion and half a carrot thinly, and crush two cloves of garlic and add these to the hot oil. Let these sear without stirring until they start to brown at the edges.
Pull the meat off the chicken, separating all of the bones from the meat. Shred the meat finely, or puree in a food processor.
Add the bones and shredded meat to the lightly browned vegetables and add 2 liters of water.
Pressure cook at high for 30 to 90 minutes, then allow to cool without venting (or vent very slowly).
Strain stock through a fine sieve.