Brown the beef chuck in batches on the stove top. Do not overcook. Add to crockpot. Add salt and pepper on top.
Add onions, carrots, and potatoes to the same pan you used to brown the beef chuck. Sauté until onions are translucent. Add garlic and sauté another 1-2 minutes.
Add flour to the vegetables in the pan and stir to coat. Slowly pour in Guinness. Continue cooking until flour is absorbed and the liquid begins to thicken.
Add vegetable and Guinness mixture to crockpot. Add peas, Worcestershire, tomato paste, thyme, and beef broth to crock pot. Mix everything together to distribute evenly.
Cook on high 4-5 hours or low -8 hours. Check on it occasionally, give it a stir and season with salt and pepper as desired. Stew is finished when a fork goes through potatoes and carrots easily and beef is tender.
If your stew is watery, thicken using corn starch slurry as described in the post above until desired consistency is reached.