There is no right or wrong way. During our intro to IDPA class we teach new shooters to use 2 hands. Open the box with your weak hand and grab the pistol with your strong. This allows you to keep the box stable while extracting the gun. If ammo is in the box or just outside of it, you can grab it with your weak hand. If you are placing ammo outside the box, don't place it where the lid will cover it when it is open. Practice this during your dry fire sessions and you will shave time.
-Capel
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