You can see that in each section, there is a small hole in the back where you can see the box through the hole. When you buy these, each hole has a pin in it, keeping the ball in the starting area. When you pull the indicator off the backing, the pins come with it. So you only have to keep it upright after you peel the backing off.

Here is a video: https://www.youtube.com/watch?v=TuLClpWRmQ8

You can see that each hole has a red colored pin in it, and you can see the pins come away with the backing (at about 0:21 in the video).