Trim excess fat from the brisket
Season both sides with salt, pepper, garlic powder, and onion powder
Sear the brisket in a hot skillet for 2 to 3 minutes per side
Place sliced onions and garlic in the bottom of the slow cooker
Add the brisket on top of the onions
Pour in beef broth, barbecue sauce, or a mix of broth and Worcestershire sauce
Cover and cook on low for 8 to 10 hours or on high for 4 to 6 hours
Check for tenderness; the brisket should shred easily with a fork
Remove the brisket and let it rest for 10 to 15 minutes
Slice against the grain or shred as desired
Spoon some cooking liquid over the brisket before serving