As you flap your way through the level, the flap counter appears above your ball. At the top you can see how many flaps you'll need to get each star.
The great thing about the Stickman Golf levels is the amount of variety in courses. Some, like the one shown here, have moving obstacles so you'll have to time your flaps perfectly.
There are tons of different themes and challenges throughout the 31 different courses. In this course, you'll need to use portals to get the ball to the hole.
The courses have wildly varying themes with different challenges in each. To unlock courses in the later levels, you'll need to have a minimum number of stars.
When you complete a hole, you're given a star rating based on the flap limit at the top of the screen (it's hard to see, but it's there in the top left).