Place the beef cubes in a bowl and toss with the flour, salt, and pepper until evenly coated.
Add the coated beef to the slow cooker along with the sweet potatoes, onion, carrots, and garlic.
In a separate bowl, whisk together the ale, beef broth, tomato paste, and thyme until smooth, then pour the mixture over the ingredients in the slow cooker.
Add the bay leaf, cover, and cook on low for 7 to 8 hours until the beef is fork-tender.
Remove the bay leaf, taste, and adjust salt and pepper if needed before serving.