Once you grab it, turn it sideways 90-degrees and the motors will immediately shut down.
I do not recommend this, because before you get to 90 degrees, the drone violently tries to right itself with full motor power - if you lose your grip that is a recipe for disaster, not to mention unnecessary stress put on the drone.
A much smoother way to do it is simply hold the left stick down for 3 seconds, the bottom sensors disable, and the drone very gently descends for you to grab. Keep that left stick down, and 1 second after that the motors shut off without any fighting or reaction from the motors.
I strictly do hand launches/catches, I find it to be the easiest way to do everything safely and consistently regardless of the terrain, I don't have to carry a bulky landing pad that blows around in the wind, and it keeps the drone much cleaner (dirt, sand, etc. are the enemy).