Season both sides of the beef brisket with salt and black pepper.
Place the seasoned brisket in the bottom of the slow cooker.
Add the chili sauce, onion soup mix, and garlic powder to the slow cooker.
Turn the brisket several times to coat it thoroughly with the sauce mixture.
Cover the slow cooker with the lid.
Cook on low for 10 hours or on high for 8 hours, or until the brisket is tender.
Once cooked, carefully remove the brisket from the slow cooker.
Allow the brisket to rest for a few minutes before slicing or shredding.
Slice the brisket against the grain for the most tender texture.
Spoon the sauce from the slow cooker over the brisket before serving.
Serve warm.