Pat the beef chuck roast dry with paper towels.
In a small bowl, combine minced garlic, chopped rosemary, salt, and black pepper.
Rub the garlic and rosemary mixture evenly over the entire surface of the roast.
Heat olive oil in a large skillet over medium-high heat.
Sear the roast on all sides until browned, about 3-4 minutes per side.
Place the sliced onion, carrots, and celery in the bottom of the slow cooker.
Place the seared roast on top of the vegetables in the slow cooker.
Pour the beef broth around the roast, avoiding washing off the seasoning.
Cover and cook on low for 8 hours, or until the beef is tender and easily shredded with a fork.
Remove the roast from the slow cooker and let it rest for 10 minutes before slicing.
Serve the sliced roast beef with the cooked vegetables and spoon some cooking juices over the top.