Choose 10 sentences from your freewriting exercise, your story, your draft, that draws your attention. Exchange your selection with someone else. Strike a third of the other person's text and rearrange the order. Give it back to the author. It's everyone's task now to write a story, where the newly selected sentences have to appear in order. (But you can write in between) Have fun!
DIFFERENT VERSION: Exchange your long text, your poem, your draft, your written observation with someone else. Now read it and strike a third of the text. Then give it back.