I also like this task because it is very clear what the student is supposed to do and it is also clear when the activity is over. Many of us have issues with students getting up and running away from work. This behavior can serve a variety of functions. It could be for attention (because they get chased when they run away) or to escape an activity (because when they run away, they are getting out of work). I have found that when students are running away for either of these reasons, they do better when two things happen.
1) Reinforcement is provided for staying at the table. Whether it is an edible, tokens, or praise..as long as it truly acts as a reinforcer for that student, it should help!
2) Students know what is expected of them. If students are provided with activities such as this one where they can see pieces disappearing (and know when they will be finished), it can help reduce problem behavior. With these students, I also set out ALL of the activities they are responsible for during that station. For instance, I may set out 2 worksheets, 1 puzzle, and 1 file folder at the beginning of our session. That way, they can see the activities they have to complete. I have seen other adults working with these students who just pull out activity after activity, and watch my students' frustration level rise, since they keep thinking they are finished....and then they have more work to do!