Season the beef brisket with smoked paprika, onion powder, garlic powder, salt, and pepper. Massage the spices into the meat for maximum flavor.
In your slow cooker, mix the sliced onions, bay leaves, thyme sprigs, beef stock, and Worcestershire sauce. Stir everything well.
Place the seasoned beef brisket into the slow cooker, ensuring it’s submerged in the liquid. Add a bit more salt to taste if you like.
Cover and cook on low heat for 8-10 hours until the brisket is tender and easily pulls apart. Aim for an internal temperature of 195 degrees Fahrenheit.
Once done, carefully take the brisket out, let it rest for a few minutes, and then slice it against the grain into thin or thick slices, as you prefer.
Serve the tender beef brisket with the flavorful onions and a ladle of the cooking liquid.
Store leftovers in an airtight container in the fridge for up to four days.