Place the beef stew meat in the slow cooker and season with salt and pepper.
Add the diced onion, sliced carrots, cubed potatoes, and cabbage wedges on top of the beef.
In a small bowl, whisk together the Irish stout, beef broth, minced garlic, tomato paste, and dried thyme until smooth.
Pour the liquid mixture over the meat and vegetables in the slow cooker.
Add the bay leaves, cover, and cook on low for 8 hours.
Remove the bay leaves, taste, and adjust salt and pepper before serving.