The false shuffle as the name implies is not actually something false or illegal. In fact, this is a technique that makes all the cards get perfectly interlaced. Hence we can say that this is more of a controlled shuffle than a false shuffle. What actually happens in this type of shuffle that the cards at the top and the bottom remain where they are. While doing so, the performer takes a bunch of cards from the bottom of the deck and keeps on putting them at the top. As the performer will show the cards before and after shuffling to the audience, they will be surprised to see that the cards will be very much in the same order as they were before shuffling. It may apparently seem difficult but practicing a few times will make it quite simple.
Put the deck in front of the audience, preferably in a horizontal position. Make sure that your performance is easily visible to your audience.
Arrange all the cards in the deck such that you have Ace through King of Spades, Ace through King of Diamonds, Ace through King of Clubs and Ace through King of Hearts.
Now grip the deck in such a way that you have the thumbs of both hands touching the one longer side of the deck and the first two forefingers of both hands touching the other longer side.
After positioning the fingers correctly, pull out a portion of cards from the bottom of the deck and put it over the top. Try maintaining some gap between the selected portion and rest of the cards in the deck.
In the same way, pull out another portion and put it on the top of the deck and continue doing the same till you have all portions shifted up. Make sure you do not forget to maintain the gap that you made in the very first shifting.
Finally, as you will turn the deck with face up before the audience, they will be surprised to see that the cards are very much in the same arrangement as they were before shuffling.