Add flour, salt, and pepper to a gallon-sized resealable plastic bag and combine. Add the beef and seal the bag. Shake until the beef is coated in the flour and seasonings.
Heat 2 tbsp of the oil in a large skillet over medium-high heat. Shaking off excess flour, add the beef and brown on all sides. You may need to do this in batches so as not to overcrowd your pan. Place the beef into the insert of a slow cooker.
Add the remaining olive oil to the skillet. Add the onion and cook for about 5 minutes, until soft and translucent. Pour in the beer and scrape up any browned bits on the bottom of the pan. Stir in the Worcestershire sauce, garlic, bay leaves, and thyme. Bring to a boil then pour over beef in the slow cooker. Cook on low for 6-8 hours, until the beef is tender.
With 45 minutes left of cooking time, add the potatoes, peas, and carrots, stirring to combine them with the beef. They should cook to fork tender in this time, but be sure to keep an eye on them so that they don’t overcook.
Taste the stew for seasoning and adjust as necessary with salt and pepper before serving.