I arrange mine to put all the keys I use on the left side of the keyboard, where my left hand normally sits. That leaves my right on the mouse, and my left to do the WASD movement, spellcasting, sneaking, and whatever else. I find it very comfortable.
Mine is similar, except that I use a mouse with thumb-buttons on the side. One of those buttons is set to "Cast," and the other is set to "Draw/Sheath Weapon." That puts all the combat functions on my right hand, and all the foot-movement functions on my left. So I can block, cast, and side-step at the same time, or whatever.