Cut up beef chuck roast into quarters. Season with salt & pepper.
Heat vegetable oil in your Instant Pot on Saute mode.
Saute beef on all sides for about 3-5 minutes each, until a nice brown sear is achieved
Meanwhile mix the remaining sesame oil, soy sauce, garlic, brown sugar, and chili oil or cayenne in a bowl
When the meat is done searing, press CANCEl on the Instant Pot and pour the sauce over the beef.
Close and seal lid, set timer on Manual High pressure to 45 minutes.
When meat is done cooking, allow to release naturally for 5-10 minutes, then do a manual quick release for remaining pressure. Remove beef from the pot and allow to cool slightly until you can shred it.
To make slow, combine all ingredients in a medium bowl and mix well.
Top warm tortillas with beef and coleslaw mix and serve immediately.