Select Sauté Function and add oil to the cooking pot. When hot, brown pork roast on both sides, about 3 minutes per side. Brown each half of the roast separately. Remove to a platter when browned.
Turn Instant Pot off and add water and liquid smoke to the cooking pot. Add browned roasts and any accumulated juices to the pot. Sprinkle the salt over the top of the pork roasts.
Select the Manual function on the Instant Pot and adjust to High Pressure. Set to cook for for 90 minutes. When beep sounds, use a natural pressure release to release pressure (approximately 20 minutes). When valve drops carefully remove lid.
Remove the meat from the pressure cooker and shred with two forks (discard excess fat as you shredded).
Add some of the juices from the pressure cooker to moisten the meat. Note: A fat separator can be used to remove the fat from the juices.