Using a large skillet over medium to medium-high heat, add a few tablespoons of oil and heat until shimmering. Pat the beef dry with paper towels, sprinkle with salt and pepper, then toss with flour until coated.
Add the beef to the skillet and cook, stirring occasionally, until browned on all sides, about 7–10 minutes. Transfer the beef to a large bowl with a slotted spoon and set aside.
Add 1–2 tablespoons of oil to the skillet. Reduce heat to medium-low and add garlic, onions, and ½ teaspoon salt. Cook, stirring regularly, until the onions are tender, about 5 minutes.
Add beef broth, chicken broth, beer, tomato paste, thyme, vinegar, and browned beef with any drippings to the slow cooker. Stir well. Add potatoes, carrots, beans, and corn, then stir again. Add the onion mixture from the skillet.
Stir until everything is combined, then cover with the lid.
Cook on high for 3–4 hours or low for 6–7 hours, until the beef and vegetables are tender. Season with salt and pepper to taste. Serve with fresh bread for soaking up the broth.