Season stew meat with salt and pepper. Brown in a skillet to get a nice crust on the meat.
While the meat cooks, whisk together soy sauce, ale and stock. Place the meat. carrots, onions and potatoes in to a slow cooker and pour liquid over the top. Top with sprigs of thyme.
Cooker 8 hours on low or 4-5 hours on high.
In the last 30 minutes of cooking turn the slow cooker to high (or leave it on high if cooking at that temp), make a slurry with the flour and water. Pour into the stew and stir. Place the cover over the slow cooker and allow to cook the remaining 30 minutes and thicken.