Season the beef chuck roast with salt and black pepper on all sides.
In a large skillet, heat olive oil over medium-high heat. Sear the roast for about 3-4 minutes on each side until browned.
Transfer the roast to the crockpot. Add the diced onion and minced garlic on top.
In a separate bowl, mix together the beef broth, pineapple chunks, chipotle in adobo sauce, soy sauce, brown sugar, ground cumin, and smoked paprika. Pour this mixture over the roast in the crockpot.
Cover and cook on low for 8 hours or high for 4 hours, until the meat is tender and easily shreds with a fork.
Once cooked, shred the beef in the crockpot using two forks and stir to combine with the sauce.
To serve, place a scoop of cooked rice in a bowl, top with the shredded pot roast, and garnish with avocado slices, fresh cilantro, and a squeeze of lime juice.