Remove the stems and seeds from the guajillo and ancho chiles. In a saucepan, boil the chiles for about 10 minutes until softened. Drain and place in a blender with garlic, cumin, oregano, black pepper, and salt. Blend until smooth, adding a bit of beef broth if necessary.

Marinate the Beef

Rub the marinade all over the chuck roast. Place it in a large bowl, cover, and let it marinate in the refrigerator for at least 2 hours, preferably overnight.

Slow Cook the Beef

In a slow cooker, add the marinated beef, bay leaves, and remaining beef broth. Cook on low for 6-8 hours, or until the beef is tender and easily shredded.

Taco Assembly

Prepare the Tacos

Once the beef is cooked, shred it with two forks. Warm the corn tortillas on a skillet for about 30 seconds on each side.

Assemble the Tacos

Place a generous amount of shredded beef on each tortilla, sprinkle with queso fresco, chopped onion, and cilantro. Serve with lime wedges on the side.