Preheat the oven to 275℉.
Using paper towels, pat the beef dry. Season generously with salt and pepper. Sprinkle and rub the arrowroot flour into the meat until it's evenly coated.
Heat the oil in a large Dutch oven set over medium-high heat. When hot, add the beef and cook until golden-brown on all sides, about 4 minutes per side. Transfer to a plate and set aside.
Reduce the heat to medium. Add the onions, carrots, celery, and garlic and cook, stirring, until the onions are tender, about 4 minutes.
Add the mustard, tomato paste, smoked paprika, bay leaves, and thyme and stir until well combined. Pour in the apple cider vinegar and cook, stirring, until the vinegar is reduced by half (leaving only a small amount of liquid in the pot).
Pour in 3/4 cup of the beef broth and stir until well combined. Bring to a boil. Reduce the heat to a very subtle simmer. Nestle the beef (and any of its juices) back into the mixture. Scatter the potatoes around the roast and pour the remaining 1/4 beef broth around the roast.
Cover with a secure lid, transfer to the oven, and roast until the beef is tender, about 4 hours for a 3-pound roast and about 5 hours for a 4 to 5-pound roast.
Remove from the oven and let cool for 10 minutes prior to serving to allow the sauce to settle. Season to taste with salt and pepper. Serve and enjoy!