I have tried resting the ball of my foot on the solid knob and tilting it to the side to push the moveable button down. Most of these controllers require the button to be pushed way down to get the machine moving. Tilting my foot not only didn't work, I got one heck of a cramp in my ankle.
So, what I do is rest my heal on the floor with the outside of my foot just behind the little toe on the button then push as needed. I completely ignore the solid knob.
That works pretty well.
Turning the controller around so you rest the heal on the body of the controller would make the cord end face you and the cord would be in the way. I can't see how that is the correct way to use it.
I have quite a few different styles of controllers and many of them have the cords entering the controller body from a point that puts it in the way. I fail to see the logic in this, but they cost too much to replace just because of that.
Joe