If you want to pose naturally, the most important thing is to relax. If you want to set up a positive photo, the most natural thing is "scissorhands". Of course, if your usual gesture habit is thumbs up, it will be natural and you won't be embarrassed to pose. Habit becomes nature, so as long as you get used to it, it is easy and natural. If you don't have any common posture, in fact, when taking a frontal photo, the most natural posture is no gesture. Stand at attention, then drop your hands naturally, curl your fingers slightly, relax, then smile and you can shoot.