Pat the roast dry with paper towels and season it all over with salt and pepper. Heat the olive oil in a large skillet over medium-high heat and sear the roast 3-4 minutes per side until browned (optional, but adds great flavor).
Spread the potatoes, carrots, onion quarters, and garlic in the bottom of a 6-quart (or larger) slow cooker.
Place the seared (or unseared) roast right on top of the vegetables.
In a small bowl, whisk together the dry onion soup mix, cream of mushroom soup, and beef broth until smooth. Pour over the roast, spreading the sauce over the meat.
Cover and cook on LOW for 8 to 9 hours (or on HIGH for 4.5 to 5 hours) until the roast is fork-tender. Avoid lifting the lid during cooking.
Move the roast to a cutting board. Shred it into large chunks with two forks, discarding any large pieces of fat. Stir the meat back into the gravy and vegetables, then serve.