Cut meat into 3 large chunks. If the pork shoulder has the rind attached, carefully remove this with a sharp knife.
Add vegetable oil to the Instant Pot, and turn on the SAUTE setting. Add the pork shoulder chunks. Saute for about 5 minutes, and turn the pork pieces to brown all sides evenly.
Remove the pork shoulder from the pot. Add water or chicken stock to the Instant Pot, and use a wooden spoon to scrape the bottom. Make sure nothing is stuck to the pot.
Add the meat back to the pot, and top with seasoning.
Turn off the saute function. Seal the lid on the Instant Pot, and turn on the PRESSURE COOK or MANUAL setting for 45 minutes. The pressure cooker will take about 5-10 minutes to get to pressure before the timer starts counting down.
Remove the cooked pork shoulder from the Instant Pot. Shred the meat with two forks.
Strain the liquid from the Instant Pot. This will remove any chunks of fat from the liquid. Discard the fat, and add the liquid back to the pot.
Add the shredded meat back to the pot. The liquid will make the meat more juicy. Add any other seasoning or sauces to taste.
Serve the pulled pork immediately.