Prepare the beef: Cut into large chunks approximately 3 inches in width. Remove any excessive hard pieces of fat.
Sear: Heat a large skillet with a tablespoon of cooking oil over medium high heat. Working in batches, careful not to overcrowd the pan, sear the meat briefly on all sides. Once seared remove from the skillet and add to a slow cooker. Continue until all meat has been seared. Pour a small amount of the beef broth into the skillet to deglaze the pan, scraping with a wooden spoon, and pour this into the slow cooker to get all the bits for flavoring.
Season: Add the seasonings into the slow cooker sprinkling over the meat: salt, black pepper, cumin, coriander, paprika, cayenne, and oregano.
Add in the quartered onion and smashed garlic cloves.
Pour the remaining beef broth into the slow cooker, just enough to cover the meat, pressing down into the broth. Add in bayleaves.
Slow Cook: Cook on LOW for 7-8 hours until meat is tender and easily shredded.
Remove the onion, garlic cloves and bayleaves. (You can serve the onion and garlic with the meat if desired.)
Remove the meat, shred and return to to the slow cooker for another 30 minutes on LOW. At this point you can taste and adjust salt or seasonings as desired.
Serve on corn tortillas with your favorite taco toppings, or inside burritos, gorditas, or tostadas.