Step 1: Build the Base. Add the onions, bell pepper, and celery to the bottom of your slow cooker. This creates a cozy veggie bed for the meat to sit on.
Step 2: Add the Roast. Place the chuck roast right on top of the vegetables, nestling it in so it’s snug.
Step 3: Mix the Sauce. In a mixing bowl, whisk together the garlic, tomato sauce, BBQ sauce, Worcestershire, beef bouillon, thyme, and water until smooth and well combined.
Step 4: Pour It All In. Pour the sauce mixture evenly over the roast, letting it seep down into the veggies.
Step 5: Slow Cook to Perfection. Cover and cook on low for 6-8 hours, or until the meat is fall-apart tender.
Step 6: Finish & Serve. Garnish with fresh parsley, then spoon everything over a big scoop of mashed potatoes. Enjoy!