In a small bowl, mix together the Italian seasoning, garlic salt, onion powder, sugar, salt, black pepper, and celery salt.
Patt the beef roast dry and rub seasoning mix all over it.
Press the saute button on your instant pot and add oil.
Place the roast in the hot oil and sear on all sides, about 2 minutes per side.
Once the roast is fully browned, turn off the Instant Pot.
Add the beef broth and deglaze the bottom of the pot, making sure to scrape any bits of food stuck to the bottom of the pot.
Pour in the pepperoncinis and juice.
Close the lid and set the pressure release valve to sealing.
Press the meat/stew setting for 60 minutes. Alternately, press the manual or pressure cook button and set to 60 minutes.
Allow the pot to natural release.
Remove the lid and shred the meat with two forks.