Turn a 6 to 8 quart slow cooker to LOW heat. Add the sliced onions, beef consomme, red wine and bay leaves to the slow cooker insert.
In a small bowl whisk together two tablespoons of flour, salt, garlic powder, thyme and oregano. Pat the beef roast dry with paper towels and sprinkle the flour and seasoning mixture over the the entire outside of the roast.
Heat the vegetable oil over medium-high heat in a large skillet. Add the roast and brown on all sides (about 4 minutes per side). Add the browned beef roast to the slow cooker. Pour the frozen carrots over the roast. Place the lid on the slow cooker and cook on LOW for 8 hours.
Remove the roast and shred the meat with forks. Remove the bay leaves and discard. Strain the broth and place the carrots and onions and shredded pot roast back into the slow cooker set on WARM.
Heat the 3 tablespoons of butter over medium heat in a sauce pan until melted. Whisk in the remaining 3 tablespoons of flour and cook for 1 minute. Whisk in the drained beef and wine broth. Cook and whisk until a gravy forms, about 3 minutes.
Serve the pot roast and cooked carrots and onions with the gravy and mashed potatoes.