The night before, thoroughly cover pork roast with salt. Keep in fridge uncovered until ready to use. Remove from fridge one hour before cooking. Alternatively, you can salt pork and use immediately, but not recommended for best flavor.
Using a very sharp knife cut slices into pork and stuff with garlic cloves.
Place trivet in pressure cooker with cup of water. Place pork shoulder in Instant Pot. Place lid on top with pressure valve set to sealing.
Set to pressure cook on high for 90 minutes.
After time has gone off manually release pressure (turn valve to venting). Check to see that pork shreds easily, indicating tenderness. If not done, return lid and pressure cook for an additional 30 minutes.
Remove pork from pressure cooker. Shred and serve immediately. If you're looking for crispy shredded pork, place the pork under a broiler for 5 minutes after shredding.