How to pump up your ass yourself at home? Provided that I'm not athletic at all? And how to make sure that the result does not disappear after pumping?

It is impossible to pump up only the buttocks so that the muscles of the legs do not turn on. Yes, there are isolation exercises, they are aimed at the gluteal muscles, but with the help of them you will not be able to significantly increase the volume of the buttocks.

Basic exercises (bench press with legs, squats, lunges, deadlift) swing the buttocks well, but include legs too. Do not be afraid of this: you are not a man, therefore it is impossible to swing huge quads without using “chemistry”.

I recommend doing such exercises at home (the technique is better to watch on the video on YouTube):

• gluteal bridge. Place a weight, such as a dumbbell, on your thighs or abdomen. Hold at the top point for a couple of seconds;
• lunges. Pick up a dumbbell or a bottle of water, another weight, walk around the apartment;
• deadlift. It is also necessary to take a load in your hands, bend over, trying to stretch the muscles of the buttocks as much as possible;
• Leading the leg back with a fitness band. Put on an elastic band on your feet in the ankle area, stand straight and take your leg back, 15-17 times each;
• squats. You also need to take the weights in your hands, squat deeply, trying to maximize the use of the buttocks.

To ensure that the result is not lost, exercise constantly, otherwise the muscles will gradually "deflate" without load.

(I am the author) I will add:
1) I would not like to gain muscle mass in my legs, since they are already slender
2) by nature, the priest is Ooooooo flat, can I still achieve, let's say, a nut ? And if so, how?