Pat your short ribs dry and sprinkle them generously with salt and pepper.
Set the Instant Pot to Sauté mode and add the olive oil. Once it's hot, add the short ribs. Sear them until browned and crispy, about 3 minutes per side. They may stick a little, but once they have a nice sear they should release pretty easily.
Remove the short ribs from the pot and set aside.
Add in the onions, celery, carrots, and minced garlic. Sauté for 3-4 minutes until they begin to soften.
Add in the red wine and deglaze the pot, scraping up any brown bits from the bottom.
Add the short ribs back into the pot along with the marinara sauce, beef broth, salt, and red pepper flakes. Give everything a good stir.
Cook on the "meat/stew" setting for 35 minutes. Let it naturally release for 30 minutes.
Remove the short ribs from the pot and place them on a cutting board or sheet pan. Shred using 2 forks and discard any bones and pieces of fat.
While you are shredding the meat, stir the sauce and set the Instant Pot to "sauté" again. Let the sauce bubble and reduce a bit for about 10 minutes. Skim any fat off the top.
Place the shredded meat back into the pot and stir. Serve tossed with gluten free tagliatelle (pictured), gnocchi, polenta, mashed potatoes, or regular pasta. Garnish with parsley and parmesan, if desired. Enjoy!