Sprinkle salt and pepper on all sides of the chuck roast. Let rest for 10 to 15 minutes while preparing the other ingredients. Thoroughly pat dry with paper towels.
Heat oil in a medium skillet over high heat until hot. Add the roast, turning occasionally, until all sides are golden brown, about 10 minutes.
Add the beef stock, soy sauce, garlic, five-spice powder, and sugar into a slow cooker. Stir to mix well.
Transfer the browned roast into the slow cooker. Arrange onions, carrots, and potatoes around the roast.
Cook, covered, on low for 8 to 9 hours or on high for 4 hours.
Slice and serve the roast with the vegetables and the sauce, or arrange them in meal prep containers for later.
