Trim excess fat from the brisket
Season both sides generously with salt, black pepper, garlic powder, and onion powder
Optional: sear the brisket in a hot skillet for 2 to 3 minutes per side
Place sliced onions, garlic, or vegetables in the bottom of the slow cooker
Put the brisket on top of the vegetables
Add 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 with a fork near the end of cooking
Remove the brisket and let it rest for 15 to 20 minutes
Slice against the grain
Serve with the cooking liquid or reduce it for a thicker sauce