Place chuck roast on a cutting board and dab both sides with a paper towel. Cut the roast into 6 even pieces and generously salt and pepper all sides.( I use almost a full tablespoon salt and about 1 teaspoon pepper.)
Heat 1 and 1/2 tablespoons of the olive oil in a large Dutch oven (or oven-safe heavy-bottomed pot) over medium-high heat. Brown the pieces on all sides for 3 minutes total. To get a good sear, don't overcrowd the meat; you can sear the meat in batches if needed). Don't skip this step. We are adding layers of flavor here. Once the meat is nicely seared with a good crust, remove the pieces from the Dutch oven and place them in the slow cooker. Use a 5-quart or larger slow cooker.
Turn heat down to medium-low and add the remaining 2 tablespoons of olive oil. Add the onion and saute for 2 minutes. Next, add in the carrots and celery and saute, stirring occasionally for 5-8 minutes. Add the garlic and saute for 30 seconds.
Turn the heat to high, add beef stock, and scrape up any browned bits. Stir and simmer for 3 minutes and then pour the stock and veggie mixture into the crockpot. While the veggies are simmering, you can add in everything else to the slow cooker: the crushed tomatoes, tomato paste, dried thyme, dried basil, dried oregano, bay leaves, and beef bouillon cube (See Note 1).
Cover the cooker and cook on low heat (high is not recommended) for 6 - 8 hours (The meat is perfect right around 7-7.5 hours -- tested in both of my slow cookers.) Remove beef, discarding any gristle or fat, and shred with 2 forks then return to crockpot.
Adjust the meat sauce's seasoning to your taste with salt and pepper. Cover and place on warm or cover and store in the fridge overnight if you're making this ahead of time.
WHEN READY TO SERVE: Bring a large pot of water to a boil. Add a tablespoon of salt and then add the pappardelle pasta* (See note 2). Cook according to package instructions but do not drain! Right before the pasta is done cooking, remove 1 cup of the pasta water.
Meanwhile, place about half of the meat sauce in a very large pan. Put over high heat. Once the pasta is cooked, use tongs to grab it straight from the pot and add to the pan. Toss the pasta with the meat sauce, slowly adding in the reserved pasta water as needed. (I'll use anywhere from 1/2 cup to the full cup.) If serving a large group, use all of the sauce.
Toss everything until you have a thick sauce that coats the pasta and the pasta water has evaporated. Serve immediately topped with fresh parsley as desired and plenty of freshly grated Parmesan cheese.