There are different options in the sand. Bunkers require club speed, loft, and entry point control. The main 2 shots are either from a fairway bunker where you are looking to get out and go a distance or from the green side bunker where you are looking for higher, softer, and shorter distance. For the fairway bunker you are looking to have the club collide with the ball first just like off the fairway. That way the energy is transmitted to the ball without any interference. As for the green side bunker the club enters the sand first and the sand transmits the energy to the ball so there is a loss of energy. This is similar to the rough where the ball comes out slower. Lets take a look at a few scenarios:
Scenario 1: Taking out the PINK box. If you are trying to help the ball out of the bunker your club could be landing too far behind the ball. With this the club is going through the sand then coming out before it even reaches the ball. The club head will probably hit the top or the middle of the ball and the ball will not come out.
Scenario 2: Taking out the blue box. In this situation you have to remove a lot of sand before getting to the ball. This will need to have a lot of speed to remove that amount of sand. Then by the time the club gets to the ball there will not be much energy or if you catch it towards the end the box the blade can come in contact with the blade. This usually results in the ball staying in the bunker.
Scenario 3: Taking out the green box. This is ideal for a green side bunker shot. The goal is to remove a sliver of sand and have the ball be in the middle of that splash. Think of it as a piece of toast in size and would be the same depth and length. This would result in more predictable shots for your golfing career. Again remember the more sand you take the more speed you need. Also the less energy is transferred to the ball. That means if one shot you take is 1/2″ deep and the next is 2″ deep the difference of energy transfer varies.
Scenario 4: Taking out the red box. This is ideal if you are trying to advance the ball a good distance just like from the fairway. The club will interact with the ball and the energy transfer is not slowed down by sand or grass. If that red box was too far forward then the club head has a high potential of colliding with the middle of the ball and would result in a bladed shot or if it is higher up a topped shot. The goal is to have the club touch the ball then the sand so the loft will get it out.
For green side bunker shots I like the 2nd from top ball. The white line is your target line, the grey line is your entry point, and the ball if just ahead of that. when training draw these lines so your body does not get too open and you can have feedback from where the club entered the sand.