Prepare the slow cooker with nonstick cooking spray.
In a gallon size Ziploc freezer bag, add the flour and 1 teaspoon salt. Shake gently to combine. Add the meat to the bag, seal, and turn until the meat is entirely coated by the flour.
In a large cast-iron skillet over medium high heat, add the oil. Carefully add about half of the meat to the skillet and brown on all sides. Remove the brown meat and place in the slow cooker to keep warm. Repeat until all of the meat is browned.
Add the onions to the skillet, and cook until softened, about five minutes. Stir often to avoid burning. Transfer the onions to the slow cooker.
Pour about one cup of the beef broth into the skillet, scraping the bottom with a wooden spoon to remove any cooked on pieces. Pour all of the broth from the skillet into the slow cooker.
Add the vegetables to the slow cooker over the meat.
In a large mixing bowl, combine the beef broth, remaining salt, garlic powder, dried thyme, black pepper, Worcestershire sauce, and tomato paste. Pour over the vegetables in the slow cooker.
Cover and cook on low for 6 to 8 hours or high for 3 to 4 hours.