Mix all the sauce ingredients together and set aside.
Cut the pork roast into three approximately even pieces. Season with salt, pepper and five spice powder.
Set the instant pot to saute and add the olive oil. Sear the pork pieces, rotating so that each side gets a crust. You can do them one at a time, but I find the instant pot can usually fit all 3.
Remove the seared pork and set aside
Transfer 1 cup of the sauce and 1/2 cup of water into the instant pot. This will deglaze the crispy bits of pork from the bottom of the pot. Use a wooden spoon or similar to scrape the entire bottom of the pot, making sure there is nothing stuck, otherwise the instant pot will give a BURN error and stop cooking.
Return the pork slices to the pot and cook on High pressure for 1 hour. Let it rest for 15-20 minutes after the timer goes off and then release the pressure valve.
Transfer the pork slices to a mixing bowl, leaving the liquid in the pot. If the pork disintegrates during this process, you know you have cooked it correctly.
Shred the pork using tongs and forks, removing any pieces of fat that haven't softened.
Add 1 cup of the pork liquid and the remainder of the sauce to the mixing bowl and toss to coat.