Make a paste of flour and water, add to stew in drips stir well until you get the consistency you like, it must be bubbling to cook the flour hope this helps!!!
i use three teaspoons of cornflour and 3 teaspoons of bisto gravy powder mix with a little water and add stirring all the time. Thats how i always thicken my gravy.
If you choose floury potatoes such as maris piper or king edward, the potatoes will fall and thicken the stew. If using other kinds of potato, and you find the stew hasn't thickened enough, one solution is to sprinkle in a little mashed potato powder, stirring all the time.