There are two main ways to obtain the three star in the stage. The first way is to aim for the ice block in the back. The second way is to aim for the pig shooting laser guns and activate the power, and aim for the laser rebound to kill the blocks in the back.
Power Activation Point
Activate the power when you are about to hit either the pig or the structure in the back.
First Shot Result
The falling blocks or laser destroy all the pigs and you will then win the three star ranking.