Season the beef cubes with salt and pepper, then toss them with the flour until evenly coated.
Heat a skillet over medium heat and brown the beef in batches, transferring the pieces to the slow cooker as they finish.
Add the potatoes, onion, carrots, and garlic to the slow cooker with the beef.
Pour the Guinness and beef broth over the ingredients.
Place the rosemary sprigs on top.
Cover and cook on low for 8 hours.
Remove the rosemary sprigs before serving.