Pat 1 (3 pound) chuck roast dry with paper towels, then season with 2 teaspoons salt and cracked black pepper all over. Heat 2 tablespoons oil in large skillet over medium-high, brown roast 3-4 minutes on all sides. Pour about 1/4 cup of beef broth in your crock, then place browned roast in crock.
In the same skillet over medium heat, sauté 1 yellow onion (sliced) until softened, about 4-5 minutes. Stir in 2 cloves garlic (minced), 1 tablespoon tomato paste and 1 teaspoon Italian seasoning. Then, pour 3/4 cup red wine into skillet, scraping off any browned bits. Allow to simmer until reduced and thickened, 2-3 minutes.
Spread onion mixture over roast in slow cooker. Combine 1 tablespoon Worcestershire sauce and 1 3/4 cups beef broth, then pour into the crock as well. Add 2 sprigs fresh rosemary and 4 sprigs fresh thyme, then cover and cook on LOW for 3-4 hours (please read notes on cooking times).
Open slow cooker and add 1 pound carrots (peeled and cut into 2" chunks), 4 sticks celery (cut into 2" pieces) and 1.5 pounds Yukon Gold potatoes (peeled and cut into large chunks) around roast. Close lid again and cook on LOW for another 3-4 hours, until vegetables and meat are tender (please read notes on cooking times).
Remove vegetables and meat and keep warm on a serving platter. Discard herbs. Combine 2 tablespoons cornstarch and 2 tablespoons cold water and stir into juices left in crockpot. Cook without the lid on HIGH for about 10-15 minutes, until thickened. You can also transfer juices with cornstarch slurry to a pot and simmer on the stove for 5-6 minutes.
Tear meat into pieces, discarding any fatty tissue. Place back on serving platter, smother in gravy and serve!