Season the beef cubes with salt and pepper, then toss them with the flour until lightly coated.
Heat a large skillet over medium-high heat and brown the beef in batches until seared on all sides. Transfer the browned beef to the slow cooker.
Add the mushrooms, potatoes, carrots, onion, and garlic to the slow cooker.
In a small bowl, whisk together the red wine, beef broth, tomato paste, and thyme. Pour this mixture over the ingredients in the slow cooker.
Stir everything gently to combine, then cover and cook on low for 7 to 8 hours until the beef is fork-tender and the vegetables are soft.
Taste and adjust seasoning with additional salt and pepper if needed before serving.