This module defines layout named OneBig. It places one (master) window at top left, and other (slave) windows at right and at bottom of master. It tries to give equal space for each slave window.

You can use this module by adding folowing in your xmonad.hs:

 import XMonad.Layout.OneBig

Then add layouts to your layoutHook:

 myLayoutHook = OneBig (3/4) (3/4) ||| ...

In this example, master window will occupy 3/4 of screen width and 3/4 of screen height.