Trim excess fat from the brisket, leaving a thin layer
Season the brisket generously with salt, pepper, and any desired spices
Optional: sear the brisket in a hot pan for added flavor
Place sliced onions, garlic, or other aromatics in the bottom of the slow cooker
Add a small amount of liquid such as beef broth, water, or barbecue sauce
Place the brisket into the slow cooker, fat side up if possible
Cover and cook on low for 8 to 10 hours, or until fork-tender
Avoid lifting the lid during cooking
Check for tenderness near the end of the cooking time
Remove the brisket and let it rest for 15 to 20 minutes
Slice the brisket against the grain
Serve with the cooking juices or reduce the liquid into a sauce if desired