Season both sides of the beef cube steaks with salt and black pepper.
Place the flour in a shallow dish and dredge each cube steak in the flour, coating both sides evenly. Shake off excess flour.
Heat the vegetable oil in a large skillet over medium-high heat. Add the cube steaks and brown them for 2-3 minutes on each side until golden. Work in batches if necessary. Transfer browned steaks to the slow cooker.
In the same skillet, add the sliced onion and mushrooms. Sauté for 4-5 minutes until softened and lightly browned. Add the minced garlic and cook for another 30 seconds until fragrant.
Transfer the onion, mushroom, and garlic mixture to the slow cooker over the cube steaks.
In a bowl, whisk together the beef broth, Worcestershire sauce, dried thyme, and paprika. Pour this mixture over the ingredients in the slow cooker.
Cover and cook on low for 6 hours, or until the beef is tender.
About 15 minutes before serving, mix the cornstarch and cold water in a small bowl until smooth. Stir the cornstarch slurry into the slow cooker to thicken the gravy.
Cover and cook on high for an additional 15 minutes until the gravy has thickened.
Serve the beef cube steaks with the mushroom gravy spooned over the top.