Trim beef of any excess fat , then season salt , pepper cumin and sazon Adjust to taste .
Heat about 2 tablespoon oil in skillet on medium, place beef in a single layer and sear meat on both sides until brown. About 3-4 minutes each side. Throw in bay leaves after browning on one side
Add remaining oil to the skillet over medium high heat. Then add onions, , garlic, bell peppers, tomatoes , tomato sauce ,thyme, paprika, cumin, and sazon. Cook for about 3-5 minutes. Add broth. Turn off heat and add 3/4 of the sauce to the slow cooker.
slow cook, until beef is tender, about 3 1/2--4 hours on High or 7 -8 hours on low, and can be easily shredded using two forks. Remove beef and set aside.
Add 1-2 cups of the sauce from the crockpot to the the remaining sauce . Cook for about 2 minutes or more . Add more seasoning (sazon ) if need. Throw in parsley. Adjust seasoning
Finally, add shredded beef and stir for a minute. Serve with rice , beans, and tostones.