This is not an official tutorial, so do not ask me for concrete explanations. I just merely took pictures of myself doing it with one hand. So, without further ado, let's get started.
Grab a stack of Chinese New Year cards (about 8-10 cards)
Start by giving the cards a bend in the center with two hands. I showed the bend in one hand because I was using the other to photograph this

Apply enough pressure with your hands to arc the cards

Hold the cards in your right hand and use your left hand to peel off one card at a time

Use your thumb and left forefinger to pinch the card that is peeled off from the pack. This creates a crease on the card

Another angle (Of course you will still be holding the stack of cards with your right hand)

Continue sliding your thumb and forefinger down the card to crease the center of the entire card

Once the first card is completed, use your other fingers to peel the second card off the stack

Finger positions to peel cards off

How to hold your cards you've already creased

Complete creasing the stack of cards

To get this

Holding the cards from the crease, you'll get this

Drop the cards one at a time into the first card (just drop, it will automatically sit into place)

Like this! It's magic!

Arrange all the folded cards in order to complete

