Assuming you are going to use your right hand to send code, the best place for your key is directly in front of your LEFT shoulder. Six or eight inches back from the front edge of your operating desk and the left edge of your key should be facing the front of the desk. Your right elbow and forearm should rest on the desktop and the key will be at your right fingertips.
A picture would be worth a thousand words!
George Allgood, W4GFA