Generously season both sides of the brisket with salt and black pepper. Place the brisket in the bottom of a slow cooker.
Add Flavorings
Add the chili sauce, onion soup mix, and garlic powder to the slow cooker. Turn the brisket several times to ensure it is evenly coated in the sauce.
Cook Slowly
Cover and cook the brisket on low for 10 hours or on high for 8 hours, until the meat is tender and cooked through.
Serve
Remove the brisket carefully, slice against the grain, and serve with the cooking juices spooned over the top.
Notes
To make this brisket gluten-free, use a certified gluten-free onion soup mix and verify that the chili sauce is labeled gluten-free. All other ingredients are naturally gluten-free.