01 - Preheat the oven to 425°F.
02 - Pat the beef dry with paper towels. Combine olive oil, kosher salt, black pepper, Dijon mustard, minced garlic, rosemary, and thyme in a bowl. Rub the mixture evenly over the beef.
03 - Place carrots, onion, and celery in a roasting pan if using. Position the beef atop the vegetables or directly on a roasting rack within the pan.
04 - Roast the beef at 425°F for 15 minutes to develop a crust.
05 - Lower oven temperature to 350°F and roast for approximately 1 hour and 5 minutes or until the internal temperature reaches 130°F for medium-rare doneness.
06 - Remove the beef from the oven, tent loosely with aluminum foil, and let rest for 20 minutes to retain juices.
07 - Discard excess fat from the roasting pan. Place pan over medium heat, pour in beef stock, and bring to a simmer. Whisk in flour or cornstarch until thickened, then season to taste.
08 - Slice the beef against the grain and serve alongside roasted vegetables and optional gravy.