Dig a hole behind the toilet to smooth the sand and cement around the geomantic omen, or is it better to leave only one side of the side wall without smoothing the cement?

First of all, it's best to stay away from the window, whether it's yours or your neighbor's. If it belongs to a neighbor, you are likely to have a conflict with your neighbor. . . Secondly, as you said, this is the only time in your life, so you'd better choose a good position before doing it ... Thirdly, as long as there are no negative substances in lime and sand, it won't interfere with Feng Shui. This is not a yin point, so there is no need to be so particular.