Let's say your driving on the right side, off your left foot. As you're ready to go up, your right hand should be directly under the ball while your left should be over the ball. As you jump, raise your left hand for protection and lay it up with the other hand. The defender will have to go through your left hand to block your shot. Practice it driving on both sides and work on your strength (pull ups, crunches, reverse crunches).
There is a variation of the overhand layup you could use. Let's say you're driving on the left side. You grab the ball with both hand as you are ready to go up and push the ball with your left hand by your ear. By doing so, your right hand elbow discourages the shot blocker to jump, and if does jump, it creates space.
On someone with a long wingspan, I would use the first move.
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