A reliable way to flip a coin

If you throw a coin with your right hand and cover it with your left and right hands, first put a coin in the palm of your left hand and remember its front and back, then take a coin with your right hand and cover it on your left hand, then throw a coin with your right hand and pretend to cover it, but in fact the thrown coin has fallen to the ground. Show him the coin that your left hand has already prepared. But pay attention to make some noise when the coin falls to the ground to cover up the sound of the coin falling to the ground. As for guessing the positive and negative coins aboveboard, it is impossible to get away with it ~ 100% right.