Add olive oil in a large skillet over medium-high heat. Pat the chuck roast with paper towels to remove any moisture, then lightly coat it with salt and pepper on all sides. Sear the roast in the skillet for about 3-4 minutes per side, until it develops a deep brown crust.

Arrange the pearl onions, baby carrots, and potatoes evenly across the bottom of the slow cooker.

Transfer the browned roast to the slow cooker, placing it on top of the vegetables.

Sprinkle the au jus mix over the roast, and drizzle the Worcestershire sauce over the top.

Add the chopped garlic around the roast and vegetables.

Place the stick of unsalted butter directly on top of the roast, and lay the thyme sprigs over the butter and vegetables.

Discard the thyme sprigs before serving. Shred the roast and serve it alongside the vegetables, spooning the gravy over the top. Enjoy!