Pat the chuck roast dry with a paper towel and season both sides with salt and black pepper.
Heat oil in a pan over high heat. Once hot, sear both sides of the roast for 1-2 minutes or until nicely browned.
In a mixing bowl, whisk together the all-purpose flour and ΒΌ cup of beef broth until smooth.
In the bottom of your slow cooker, add the flour mixture, the remaining beef broth, tomato sauce, garlic, thyme, rosemary, paprika, mustard powder, and additional salt and pepper. Give it a good stir.
Add the seared beef, chopped carrots, onions, and quartered potatoes to the slow cooker. Stir to coat everything in those delicious flavors.
Cover the slow cooker and set it on HIGH for 4-6 hours or LOW for 8 hours.
Once done, you can store the leftovers in the fridge for up to 4 days or in the freezer for up to 4 months.