Begin by seasoning the chuck roast generously with salt and pepper on all sides.
In a large skillet over medium-high heat, sear the roast on all sides until browned. This should take about 3-4 minutes per side. Transfer the roast to the slow cooker once browned.
In the same skillet, add the onions and garlic, sautéing for about 2 minutes until fragrant. Then, pour in the beef broth, Worcestershire sauce, and soy sauce, scraping the bottom of the skillet to deglaze.
Pour the mixture over the roast in the slow cooker. Add in the carrots, potatoes, thyme, and rosemary.
Cover the slow cooker and set it to low for 8 hours or high for 4 hours, depending on your schedule. The meat should be fork-tender when ready.
If you would like a thicker gravy, mix the cornstarch and water in a small bowl to create a slurry. About 30 minutes before serving, add the mixture to the slow cooker and stir gently, allowing it to thicken.
Once cooked, remove the roast and vegetables from the slow cooker and let them rest for about 10 minutes.
Slice the roast against the grain and serve it on a platter alongside the carrots and potatoes, drizzling some of the gravy over the top.
Notes
Arrange the sliced roast in the center of a large serving platter, surrounded by potatoes and carrots. Garnish with a sprinkle of fresh parsley for a pop of color. Serve with extra gravy in a small bowl on the side.