Just follow the practice in Baidu Encyclopedia. The methods of standing piles are all safe, generally not easy to deviate, and you can "stand stupidly" without any theoretical knowledge. As long as you keep a normal mind, there will be no problem. As for the problem, you can stand and think, because some things will not be understood until you really do it, which is a bit different from reading.

The specific requirements for standing piles can be found in the book Principles and Methods of Quietly Practicing Health, written by Lu, in which the posture of practicing Qigong is described in detail. You can find it on Baidu, and there is a PDF version on Douding's website. There is also the "horse stance just look" standing pile in Shaolin Neijin Yizhichan, and it also tells how to stand the pile and how to follow it.

As for the bad stomach, it is suggested that the immortal rub his abdomen and rub his abdomen.