This is how I practice the piano. I have an old fashioned kitchen timer, which I set for 20 minutes, and I don’t do anything but play the piano for those 20 minutes. It works beautifully, and often I keep playing beyond those initial 20 because I’m having so much fun. I had no idea that this was a thing with a real name and practitioners! I’ve been doing this since I was a little kid. It definitely works.