Trim the roast to remove any skin and the top layer of fat. Pat dry.
Mix the dry rub ingredients in a small bowl. Rub the seasonings all over the pork, coating well.
Turn on saute mode on the Instant Pot . Add the cooking oil to the pot. When hot, add the pork roast and brown on both sides (if possible). Turn off the Instant Pot and remove the roast.
Add the broth and whisk any browned bits from the bottom of the pot. Place the trivet into the pot and lay the pork roast on top of the trivet.
Cover the pot, lock on the lid, and make sure the valve is set to sealing. Press the pressure cook button and set the cook time to 45 minutes. Note that the time will vary for larger/smaller or leaner cuts. See notes before proceeding.
When the cooking cycle is finished, allow the pot to depressurize naturally for 10-15 minutes, then move the valve to venting to release the remaining pressure.
To make the gravy, first skim excess oil from the top of the broth in the Instant Pot. Make a cornstarch slurry by adding the cornstarch to cold water. Turn on saute mode. When the liquid is boiling, add the cornstarch and whisk until thickened.
Slice the roast and serve with your favorite side dish.