I have read on a few websites that if you have not got the ice water achievement this wont unlock. I know I had to get Ice water first before I got game over in a flash to unlock. This might not be the case for some people but it’s something to keep in mind.
To get game Over In A Flash set the clock to 2 minutes. If you want turn off fouls just in case something goes wrong while trying to get this. Make sure also to turn off the shot clock. With the shot clock turned off you just have to hold on to the ball and never shoot. When the other team gets the ball after one of the half’s try to steal the ball or force a bad shot. Of course if they make it you have to score to. Repeat until second overtime. Now in the second overtime, once you have the ball with the score tied hold on to the ball until time is just about to expire at 1.5 or less and shoot. If it goes in you should get the achievement a few seconds after. That is pretty much the easy and sure fire way to get this achievement.