Add sliced onions, celery, carrots, and potatoes to a 1.5 or 2-quart slow cooker.
In a small bowl, mix together pepper, Italian seasoning, garlic powder, onion powder, and salt.
Pat the beef dry with paper towels. Rub the seasoning mix evenly over all sides.
Heat oil in an 8 or 10-inch skillet over medium heat. Use slightly less oil if using an 8-inch skillet. Sear the beef until golden brown on all sides, about 2 minutes per side. Transfer to a plate.
Cut 1-inch deep slits across the top of the roast with the tip of a sharp knife. Widen each slit with your finger and press a garlic clove in as far as it will go.
Place the beef on top of the vegetables. Pour the broth over everything and cover with the lid.
Cook on low for 8 hours or on high for 4 hours.
In a small bowl, whisk the cornstarch and cold water together until smooth to make a slurry.
Transfer the beef to a plate. Stir the cornstarch slurry into the broth until smooth. Return the beef to the slow cooker, spoon gravy over it, cover, and cook on high for 15 minutes to thicken.Pro Tip: If the gravy is too thin, whisk more cornstarch with cold water, stir it in, and cook until it reaches the thickness you want.
Use two forks to shred the beef, then stir it into the gravy.
Spoon the pot roast and vegetables into a bowl and serve.
Notes
Don't skip the sear. Searing the beef before it goes into the mini crock pot is what builds flavor. That golden-brown crust on the outside is what gives the finished roast its deep, savory taste. A slow-cooked roast without searing tastes flat.Low and slow beats high and fast. This slow cooker pot roast for one cooks in 4 hours on high or 8 hours on low. I prefer low every time. The longer the beef cooks at a lower temperature, the more the connective tissue breaks down, and the more tender the finished roast.Use a 1.5 or 2-quart slow cooker. Anything larger and the liquid spreads too thin, which means less flavor in the braising liquid and a drier roast. A mini crock pot keeps everything in close contact with the broth.Let the seasoned beef rest before searing. After seasoning, let the meat sit at room temperature for 10 to 15 minutes. This helps the salt penetrate the surface and gives you a better sear.Mix cornstarch with cold water, never hot. Hot liquid causes the starch to clump before it dissolves. A cold-water slurry stirred into hot broth gives you a smooth, lump-free gravy every time.Store leftovers properly. Keep leftover pot roast in an airtight container in the refrigerator for up to 3 days, or freeze for up to 3 months. The flavor actually improves on day two as the beef continues to absorb the gravy.If doubling this recipe, cook in a 3 or 3.5 quart slow cooker.