Cut the pork into several pieces so that it fits into the Instant Pot below the fill line. Season the pork with salt and pepper, then brown it on all sides on the searing or frying setting.
Add the onion, celery and carrot around the pork and cover with chicken stock keeping below the fill line. Add the lid to the pot and make sure to turn the steam release vent to the sealing position. Cook on manual for 1 hour. Let the pressure release naturally for 10 to 20 minutes
Remove the pork and slice or shred, add any sauce you like. I use plain shredded or sliced pork for my Cuban Sandwiches.
The meat freezes well for up to 6 months.