Heat the olive oil in a large skillet over medium-high heat. Season the beef chuck roast generously with salt and black pepper, then brown on all sides for about 8 minutes total, until deeply colored.

Remove the stems and seeds from the dried guajillo chiles and dried ancho chiles, then toast them in a dry pan for 1-2 minutes. Toast until fragrant and slightly darkened, then transfer to a blender.

Add beef broth, apple cider vinegar, garlic, cumin, oregano, cloves, cinnamon, and black pepper to the blender. Blend until smooth, aiming for a thick, cohesive mahogany-colored paste.

Place the browned beef in a slow cooker and pour the chile mixture over it, so the meat is well coated. Add the bay leaves on top for aroma.

Cover and cook on low for 8 hours, until the beef shreds easily with a fork. The sauce should look glossy and deepen to a rich mahogany color.

Shred the meat directly in the slow cooker and stir the shredded beef to mix evenly with the sauce. Stir until the sauce clings to each strand.

Add the juice of 2 limes and stir again so the citrus brightens the flavor. Rest the barbacoa uncovered for 10 minutes to thicken slightly before serving.

Serve the barbacoa warm as a taco filling with tortillas, onions, and cilantro. Spoon it over warm tortillas and let the glossy sauce pool and cling to the meat.