This is the 4760th most frequent German word.
zusammensetzen
To assemble or put together.
Here, 'zusammensetzen' refers to the action of putting the puzzle pieces together to form a complete picture.
Wir müssen das Puzzle zusammensetzen.
We need to assemble the puzzle.
In this context, 'zusammensetzen' is used metaphorically to mean that members of the commission will come together or meet to discuss.
Die Kommission wird sich nächste Woche zusammensetzen.
The commission will convene next week.
Here, 'zusammensetzen' is used as a reflexive verb to indicate the components making up a certain group or entity.