SEARING THE MEAT: Take the beef chuck roast and using a small paring knife, make 3 small 'x' marks into the meat. Take 3 cloves of garlic and insert them into the 3 'x' marks so that the clove is completely inserted into the thickness of roast. Season both sides of the meat generously with salt and pepper. Heat the oil in a large, deep skillet or do this directly in your saute pan for the pressure cooker. Add the beef in one piece and fry on each side for 5 minutes, turning only when the exterior is browned. This will splatter a bit but don't cover the pan as the meat will end up steaming rather than searing.
SLOW COOKER: Chop the remaining 3 cloves of garlic into thin slices and add to the slow cooker along with all the remaining ingredients. I used a 6-quart slow cooker but a 3-quart slow cooker will work too. Cover and let cook on the low setting for 7-8 hours.
INSTANT POT: Once the beef has seared, remove it to a plate and saute the onions, peppers, and garlic in the remaining oil for 30 seconds. Add all the remaining ingredients and cover. Set the pressure cooker to cook for 20 minutes per pound. My roast was 2.5 pounds, so I did this for 50 minutes. Once the timer goes off, allow a natural pressure release.
SHRED: Shred the beef with the forks and give it a stir. If it doesn't, slow cook or pressure cook for additional time as needed. Taste for seasonings, season with additional salt and pepper as desired.
TO SERVE: Serve over a bed of rice with cuban-style black beans on the side topped with additional cilantro and a few lime wedges. You can also use the shredded beef for burritos, breakfast quesadillas, or tacos! The possibilities are endless!
