How do you make the flap t sound as in the words city and letter

I’m having a hard time figuring out the right placement and motions of the tongue when making this consonant. I watched a few videos on this topic. People say that in order to make the sound you don’t want to be touching the roof of your mouth too much but you have to lightly bounce the tip of your tongue against the roof of the mouth. I have no idea how to do this. I tried doing it and I either touch the roof of the mouth too hardly and it sounds heavy and unclear or in effort to touch lightly, I end up accidentally pulling my tongue away and it doesn’t even reach the place that it should. I would be really grateful for an explanation of what is that that tongue is doing when you make this sound. Thank you for the answers in advance!