garyk49:
To get the flop to go straight... hit the line before the ding, and aim at the hole. Taking the green slope into consideration.
If hitting the ding line, aim to the left of the hole as the ball will come off to the right. Backspin will work better when hitting the ding, so take that into account.
I believe hitting before the ding gives the same result as aiming to the left of the hole.
A flop shot always goes left to right, therefore, either may work. If you are an "off ding" player than go with Gary's method. The only problem I see is hitting at the right place, before the ding, is just as difficult in hitting the ding. If you simply aim a few yards left of the hole, you will still be safe whether you miss the ding too early, or too late.
For examples of playing the ball to the left of the pin, which result in many hole ins, watch some of the videos Sam has linked to above. In all the flops, I am always using reverse cam (ALWAYS when hitting a flop), aiming to the left, adding a few more feet than needed and apply some back spin - (remember, this shot will result in birdies and eagles if done right so, REMOVE THE FLAG!)
You will see, even when I miss the ding, I still get good results.
I am certainly not as good as most here, but the above works for me.
Here is an example: