Victor,
Square is worse than nearly square, so you should be going away from square, not toward it!
I usually recommend not facing a corner because that puts another corner behind you which focuses reflections toward you. If the wall behind you is flat, as in the drawing, it's probably not so bad. But I would not take a small room and make it even smaller by walling off half of it as shown!
This article shows the best way to set up in a rectangular room:
RealTraps - How To Set Up a Room
--Ethan