Preheat grill to medium-high heat. While the grill preheats, add half of the chopped carrots and celery to a roasting dish, sprinkling them with flour. Set aside.
Start your pot roast on the grill and finish it in the oven for pot roast that is smoky and succulent. Think old-fashioned flavor that is boosted by the smokiness of the grill.
Season both sides of the roast with salt, pepper, garlic and onion powder.
Place over the roast on the grill over direct heat, cooking until well browned . This should take about 10 minutes. Using tongs, flip the roast over and cook the second side until well browned. This should take an additional 10 minutes.
Transfer the roast to the prepared roasting pan, placing it on top of the carrots and celery. Preheat oven to 300°F.
In a measuring cup, blend the beef broth, wine and Worcestershire sauce. Pour over roast in pan. Combine English Rub and thyme leaves. Sprinkle half over roast. Add salt to taste.
Cover the roasting dish with its lid. Cook for 15 minutes. Then, reduce heat to 275°F, cooking for 2-1/2 hours.
Remove roast from the oven. Carefully lift the lid and place the remaining carrots and celery, shallots, onions, bell peppers and potatoes around the roast. Tuck bay leaf between the veggies and roast. Sprinkle vegetables with remaining herb mixture and season to taste with kosher salt and pepper. Add 1 cup water if needed to keep the roast and vegetables moist and make a pan sauce.
Cover the dish and return to the oven. Continue cooking for another 1 to 1-1/2 hours or until the vegetables are soft and the meat is fork tender.
Transfer vegetables to a medium bowl. Move pot roast to cutting board. Tent with foil and let rest for 15 minutes. Carve into slices and serve with roasted vegetables and pan juices.