"A player is entitled to place his feet firmly on the ground when taking his stance, but may not establish a stance."²
The rules of golf therefore allow the golfer to place his feet as he needs to in order to have a firm and stable stance. However, the player must ensure that he does not change the position of the ball. He must not press down or step on any obstacles by assuming the stance before the golf shot. This would lead to an improvement in the ball position and would result in corresponding penalty strokes in accordance with the official golf rules of the German Golf Association. Incidentally, it is also permitted to take a firm stance in the bunker. You can literally dig your feet into the sand.
Status: 2018