Step 1 : Split your deck into two relatively equal piles.

Step 2 : Grasp the bottem of the cards with your 3 last fingers(including pinky), place your index finger on top of the pack and place your thumb on the ruffling edge and bend them up.

Step 3 : Move the two packs close to each other and slowly let each bent up card fall under and on top of the previous card. Do this untill the deck is fully shuffled like here.

Step 4 : Keep both decks in the state shown above and bend them upwards or downwards in an arch like formation. Using your fingers to push the cards up or down.

Step 5 : Release the upwards/downwards pressure on the cards to watch the cards flourish back into the normal pack state.

Finished Manouver.
Sorry for bad qualiy my phones shit.