Rinse, dry and cut the meat. In a bowl, toss together with the seasoned flour and remove, shaking off the excess.
Pour enough oil in a large saute pan to lightly coat the bottom of the pan, then heat the cooking oil over medium-high heat. When the oil is hot, add half of the meat in a single layer in the pan and sear the meat on at least two sides (about a minute per side). Remove from pan to a plate or bowl and repeat with the rest of the floured meat. Set seared meat aside.
Lower the heat to medium. If necessary, add a little more oil to the pot and saute the onion, bell peppers, and spice pack. Stirring often, cook until the vegetables just begin to soften, then and add the garlic and tomato paste, stirring to fully incorporate. Let cook for a few more minutes.
Add the browned beef to the slow cooker, then pour in the sauteed vegetables, Cookin' Sauce, broth, and tomatoes with their liquid, and the bay leaf. Cook on the low heat setting for 10-11 hours, or the high heat setting for 5-6 hours. Stir in the Finishing Sauce. (Note: for a spicier sauce, use all of the Finishing Sauce; use half the pack for a milder sauce.)
Optional: To thicken the 'gravy' sauce, remove the meat with a slotted spoon to a large bowl. Cook the sauce in the slow cooker uncovered for about an hour, stirring occasionally, until it has thickened. Season to taste with salt and pepper if needed.
Serve with warmed tortillas, cotija cheese, cilantro and lime wedges.