Start by removing the seeds and veins from the dried chiles. After toasting them until fragrant in a dry pan, let them soak for 20 minutes in hot water.
Blend together the soaking chilies, onion, garlic, cumin, oregano, salt, pepper, vinegar, and bay leaf in a blender. Process till smooth.
After chopping the steak, season it with salt and pepper. In a heated pan, sear the meat until browned all over.
Spoon the seared meat into a big pot or slow cooker. Cover the meat with the chili sauce.
Cook until the meat is soft and easily shreds, 6 to 8 hours on low heat (or 3 to 4 hours if using a pressure cooker).