Rinse roast with water and place in slow cooker.
Pour on the Guinness and let the meat soak it all in while you chop veggies and measure spices.
Throw veggies in with the roast, then mix together beef broth, Worcestershire, and minced garlic. Pour mixture on top of everything and toss in the bay leaf. Make sure roast is completely immersed in liquid. (If it's not, you can either turn it over a few times throughout the day if you're home, or just pour in some more Guinness.)
Cover and cook on low for 6-8 hours. Serve with a loaf of crusty bread and gravy (below).
OPTIONAL GRAVY: Ladle out 1 cup of juices from slow cooker into small saucepan. Mix in 2 tsp. cornstarch, 1/2 tsp. garlic powder, 1/4 tsp. dried sage powder, and salt and black pepper to taste. Bring to a simmer stirring constantly. Simmer until thickened (about three minutes).
I made this recipe using a smaller sized (1 lb.) roast, but it will work fine without tweaking for up to 1 1/2 lbs--just make sure there's enough liquid to cover all the meat and add salt to taste.