Provide each student with a 7-piece tangram set or a copy of the puzzle made out of paper or cardboard.
Ahead of time, create overhead shadow or outlines of possible puzzles that students can create using all 7 pieces of the puzzle. (You can create these using a Tangram puzzle book, or you can create designs and shapes and then trace around the outer edge with a marker onto the overhead.)
Show just one puzzle at a time. Students must try to duplicate the puzzle during the 10 to 15 minutes allotted. This would make a great "Bellwork" activity for those first few minutes of the day when attendance, etc. has to be accomplished.
Students attempt to make the puzzle and then when the time is up, a volunteer must come up to the overhead and recreate the Tangram puzzle for all to see using his/her puzzle pieces.
This is a great idea for improving reasoning skills, problem solving, and for learning to manipulate materials.
If time, and students have not lost interest, you could go on to another puzzle. Puzzle pieces could be stored in plastic baggies for reuse at other times. This would even be a great filler for use when extra minutes occur at the end of lessons, before lunch, at the end of the day, etc.
There are many books on Tangrams that can be great sources of inspiration for this activity. Check book stores and game stores for books on this topic.