There are no difficult bunkershots, only bad thinking!
When it comes to bunkershots, like all other shots in golf, there are no difficult shots, only bad thinking which make the shots difficult. If you instead can turn a difficult position (impossible to most people) and instead see a possibility to show your mates what you're made of.
There's always a chance to get the ball close to the hole or even in the hole and it's the attitude that's the most important part.


Tips for the less easy shots:

Uphill
In a uphill position the thing is to lean a bit backwards towards the right foot to even out the stance, making it paralell to the ground. Since you get more weight on the right foot the ball is adressed just infront the middle (not to the left like in a flat position). And since the angle on the swing gets steeper down towards the tilt of the sand it's important to be extra careful to make sure you follow through.


The ball above the feet
When the ball lies close to the fringe of the bunker and the feet are far below the ball you need to even out the stance by shortening the grip enough to be able to stand ridgid and comfortable.There's a risk of hitting too much sand, so make sure to have the center of gravity back on your heels and follow through thoroughly.


The ball below the feet.
In Scotland there are a lot of "pot"-bunkers that are deeper and most often the ball needs to be played to the side from a position where the ball is located below your feet. In this case the thing is to lenghten your arms as much as possible and gripping high on the club. There's a tendency of topping the ball (hitting the top of the ball with the bottom of the clubface) hence it's extra important to hang down with the upper body throughout the entire swing. Weight on your toes and try hitting deeper in the sand.