1Pat the flank steak dry and season it generously with salt and pepper.
2Heat the olive oil in a skillet over medium-high heat. Sear the steak pieces for 3 to 4 minutes per side until deeply browned, then move them to the slow cooker.
3In the same skillet, cook the onion and both bell peppers for about 4 minutes until just softened. Stir in the garlic, cumin, oregano and smoked paprika and cook for 30 seconds until fragrant.
4Pour in the tomato sauce, beef broth and red wine vinegar, scraping up the browned bits from the pan. Pour everything over the beef in the slow cooker and tuck in the bay leaves.
5Cover and cook on low for 8 hours, or until the beef shreds easily with a fork.
6Near the end of cooking, cook the white rice according to the package directions.
7Remove the bay leaves. Shred the beef right in the cooker with two forks and stir it through the sauce. Fold in the olives and let everything sit for 10 minutes so the beef soaks up the sauce.
8Taste and adjust with salt, pepper and a splash more vinegar if you like it brighter. Serve over the rice and top with cilantro.