Copy Sergio Garcia’s sand technique.
I see a lot of amateurs set up poorly in the sand, especially with their lower bodies. They stand with their legs fairly straight and their body weight equal on both feet, like they would for a normal iron shot. But when you do that in the sand, you tend to fall back on the downswing and hit way behind the ball, or else thin it.
Instead, copy Sergio Garcia ( above). He’s a very good bunker player, and a lot of it has to do with his setup. Not only does he favour his front foot when he addresses the ball, he gets into a wider stance with his knees noticeably bent and facing towards the target. This lower and wider stance keeps his lower body stable and allows him to hit down and through the sand starting just behind the ball. And pointing the knees somewhat towards the target helps him complete the swing, keeping the clubhead moving well past impact. The result is a textbook bunker shot.
Sergio does a great job of driving the club through the sand.