PREP: Cut the beef chuck roast into 1-2-inch cubes and set aside. Toss beef cubes with salt and pepper to taste; I add 2 teaspoons fine sea salt and 1-1/2 teaspoons pepper.
SEAR BEEF: Heat a large cast iron pot or regular pot on high (cast iron is best!) Add in 2 tablespoons olive oil. Once the pot is hot, add a single, spaced-out layer of cubed beef pieces (don't overcrowd the beef, so we can get a nice sear. That char = flavor!). Sear beef for about 2 minutes per side (Don't stir the beef around, simply leave it in one spot and then, using tongs, flip it to the other side after about 2 minutes -- it should release and be very easy to flip). Sear beef in batches adding extra olive oil if needed. Once a batch is seared, remove it with tongs into a bowl and set aside for now.
GRAVY: Do not wash out the pot -- we've got loads of flavor here! Add the remaining 1 tablespoon of oil. Add in the diced onions and cook, stirring constantly, for 4-6 minutes, or until beginning to soften, scraping up the browned bits in the pot as you stir the onions. Then add in the garlic and cook for another 30 seconds or until fragrant. Add in the butter and allow to melt. While whisking constantly, add in the flour and, whisking constantly, cook for 1 minute. Pour in the wine (or stock if using) while whisking constantly until you get a thick sludge and the liquid has reduced. Then add in the beef stock, gradually, while whisking constantly. Simmer over low heat until thickened, about 2-3 minutes. Remove from heat and scrape every bit of this mixture into the slow cooker.
SLOW COOKER: While you're working on the beef or gravy, add the remaining ingredients to a 6-quart slow cooker: the halved baby carrots, sliced celery, fire-roasted diced tomatoes (don't drain), tomato paste, dried parsley, dried thyme, bay leaf, Worcestershire sauce, and sugar. Add in the set-aside beef and any accumulated juices. Give everything a good stir and submerge the beef pieces under the liquid.
COOK: Cover and cook on low for 8-10 hours or high for 6-7 hours. (I highly recommended cooking on low.)
GNOCCHI: About 20 minutes prior to serving, bring a large pot of salted water to a boil and cook the potato gnocchi according to package directions (~2-3 minutes). Drain and set aside. Don't rinse under cold water.
FINISHING: Give the stew a good stir and taste for additional seasonings if needed (salt, pepper -- I typically add another 1/4 teaspoon each) even an extra pinch of sugar goes a long way! Serve the stew in bowls and stir in a few spoonfuls of gnocchi into each bowl. Garnish with fresh thyme or parsley (if using) and serve with crusty warmed bread!