Press the *saute* button of your instant pot to let it warm up, once the screen says *hot*, add olive oil to the pot. Rub the roast with salt and pepper and sear in the pot on all sides. About 4 to 5 minutes total.
Add the stock to deglaze the pan seal the Instant Pot. Press the *manual* button and use the + to choose 45 to 50 minutes pressure cooking time, depending on the thickness. Use this cooking time to prep your vegetables.
When time is up, use the Quick Pressure Release to release the steam. Once done, quickly remove the lid and add in the potatoes, carrots, celery, and seasoning.
Close and lock the lid and use the + button to select 10 minutes of pressure cooking time. Once time is up, use the Quick Pressure Release to release the steam.
Once the release is complete, you can either remove the roast if you'd prefer to slice it, or you should be able to use tongs to pull it apart right in the pot. Either way, add the butter to the pot and stir to melt. Spoon vegetables and gravy over the sliced roast or spoon into a bowl if doing shredded roast. Garnish with parsley if desired.