Preheat oven to 350 degrees.
Season the chuck roast with salt and pepper. Dust all sides of the roast with flour; set aside.
Heat a large, 5-quart cast iron Dutch oven over medium heat. Add oil and heat until the oil just begins to shimmer, add the roast and sear on all sides until a deep golden-brown color. Remove the roast to a platter and set aside.
Add quartered onion, garlic cloves, thyme, marjoram, wine, beef stock and chicken stock. Bring to a boil, use a wooden spoon to scrape up the fond developed at the bottom of the pan. Return the roast to the pot and cover.
Place covered dish in a preheated oven and continue to braise for 2 ½ hours.
Add potatoes and carrots, return to oven, and continue to cook for an additional 30 minutes or until the vegetables are tender.
Remove pot roast from the oven. Transfer the roast and vegetables to a serving platter, tent with foil to keep warm. Skim excess fat off the surface. Discard sprig of thyme. Bring the liquid to a simmer and reduce to thicken. Taste and season with additional salt and pepper if needed. Nestle the meat and vegetables back into the pot. Serve family style with a crusty loaf of bread.