How many balls out of a set number bowled can the batsman manipulate into the gaps.
Ask player to think about how they could get the ball into the gap whilst still keeping the maximum amount of bat presented to the ball. You can get the ball safely behind square simply by playing it late.
Can the batsman manipulate the balls into the gaps in a set order, i.e. work around the gaps in a clockwise fashion. Count how many times in a row they hit the gaps.
Discuss the role of the feet in trying to manipulate the gaps. Lining up the feet towards the target will give a better chance of success.
Set up a leg-side, or off-side dominated field, whereby there are three gaps on one side and only one gap on the other. See how successful batsmen are at manipulating to different sides of the wicket.
Set specific targets for the players to work towards. i.e. count how many times out of ten deliveries the batsman successfully finds the gap, so that they can be competitive with themselves and other team members