In a large bowl combine all the spices with the olive oil and red wine vinegar. Add the chuck roast and garlic turning the beef multiple times to make sure it is fully coated. Cover and allow to marinate for at least 4 hours up to overnight.
Place the chuck roast into the slow cooker along with 1 cup of water. Seal the lid on top of the Instant Pot. Set the cook time on Manual for 90 minutes on High. Allow the pressure to release for 10 minutes once the beef has cooked.
Remove the beef to a rimmed baking sheet or bowl and shred with two forks. Add about ½ cup of the reserved cooking liquid to the shredded beef. Season the beef with salt and pepper to taste.
Build sandwiches by spreading hummus on the pita. Top with beef and add garnishes to your liking.