In a large skillet, heat olive oil over medium-high heat. Season the beef roast generously with salt and pepper. Sear the roast in the skillet, cooking for about 4-5 minutes on each side until browned.
3-4 lb beef sirloin tip roast, 2 tablespoons olive oil, salt and black pepper
Place the chopped onion, garlic, carrots, and celery at the bottom of the slow cooker. Position the seared beef roast on top of the vegetables.
1 cup onion, 4 cloves garlic, 4 large carrots, 4 celery stalks
Pour the liquids and dried herbs.
1 cup beef broth, 1 cup red wine, 2 tablespoons Worcestershire sauce, 1 tablespoon soy sauce, 1 teaspoon dried thyme, 1 teaspoon dried rosemary, 2 bay leaves
Cover the slow cooker and cook on LOW for 6-8 hours, or until the beef is tender and can be easily shredded with a fork.
For a thicker gravy, mix cornstarch with water in a small bowl to create a slurry. About 30 minutes before serving, remove 1 cup of the cooking liquid and stir the slurry into it. Return the mixture to the slow cooker, stir, and continue cooking until thickened.
2 tablespoons cornstarch, 2 tablespoons water
Before serving, remove the bay leaves and any cooking twine. Slice the roast and serve with the vegetables and thickened sauce from the slow cooker.