Heat olive oil in a large skillet over medium-high heat. Add the flank steak and sear each side for 3-4 minutes until browned. Transfer the steak to a slow cooker.
In the same skillet, add the onion and bell peppers. Sauté until they begin to soften, about 5 minutes. Add the garlic, cumin, oregano, smoked paprika, and black pepper, and cook for an additional 2 minutes.
Transfer the sautéed vegetables to the slow cooker over the steak. Add the diced tomatoes, apple cider vinegar, bay leaves, and salt. Stir to combine.
Cover and cook on low for 8 hours or on high for 4 hours, until the beef is tender and shreds easily.
Once cooked, remove the beef from the slow cooker and shred it with two forks. Return the shredded beef to the slow cooker and mix with the sauce.
Preheat the oven to 400°F (200°C). Toss the jicama slices with avocado oil, salt, and pepper. Spread them out on a baking sheet in a single layer.
Bake the jicama for 25-30 minutes, flipping halfway through, until they are golden and crisp on the edges.
Serve the Ropa Vieja hot, topped with the baked jicama slices as a plantain alternative.