Add remaining 1 tablespoon oil to pan; swirl to coat. Add onions and garlic; sauté 4 minutes. Add beer, scraping pan to loosen browned bits. Bring to a boil; cook 2 minutes. Stir in 1 cup stock, remaining 1 1/4 teaspoons salt, and remaining 3/4 teaspoon pepper. Bring to a simmer. Carefully pour mixture into a 6-quart electric slow cooker. Add beef, potatoes, carrots, thyme, and bay leaves. Cover and cook on LOW for 7 hours.