Lock the Instant Pot lid into place. Use the manual setting to choose High Pressure for 45 minutes, bringing the Instant Pot to full pressure.
When the timer sounds, use a natural release for at least 20 minutes, allowing the pressure in the Instant Pot to gradually come down on its own.
Place the shredded beef into a hot skillet over medium high heat; add some of the reserved cooking liquid to the meat to make it a nice juicy consistency. Serve the beef over warm rice, topped with Corn Salsa.
Combine all salsa ingredients in a bowl.
If you opt to leave the chuck roast in one big piece of meat instead of cutting it into chunks as per the directions here, be sure to increase the pressure cooking time by 25-30 minutes. Cutting the roast into chunks allows for more browning surface and also helps the roast cook much faster.