Heat the olive oil in a skillet over medium heat. Add the stew meat and brown on all sides.
Add the diced onion and minced garlic to the skillet. Cook for 2 minutes until the onion softens.
Sprinkle the flour over the meat and stir to coat everything evenly.
Transfer the mixture to the slow cooker. Pour in the Guinness and beef broth, then stir in the tomato paste, thyme, and bay leaves.
Add the cubed potatoes, sliced carrots, and chopped cabbage. Stir gently to combine.
Cover and cook on low for 8 hours.
Remove the bay leaves, season with salt and pepper, and serve.