Rinse the dried chiles, then add them to a saucepan with 2 cups of the beef broth, along with the onions and garlic. Bring to a boil, then reduce to a simmer and cook uncovered for about 20 minutes, until the chiles are softened.
While the chiles are cooking, heat the oil in a large skillet over medium-high heat. Once hot, sear the beef in batches until browned on all sides. Transfer the seared meat to your Crockpot.
Remove the chile mixture from the heat and pour in the remaining beef broth to help cool it slightly. Transfer everything to a blender or food processor and blend until smooth to create a rich red chile sauce.
Pour the sauce over the beef in the Crockpot. Add the salt, pepper, Mexican oregano, cumin, chili powder, smoked paprika, cinnamon, and bay leaves.
Cover and cook on low for 7–8 hours or high for 4–5 hours, until the beef is tender.
About 30 minutes before it’s done, stir in a cornstarch slurry to thicken the sauce. Cover again and let it finish cooking until the sauce has thickened. Remove and discard the bay leaves before serving.