WEX is writing time. Sometimes we have a prompt and have to use the prompt to write a story that is at least one whole page long. But sometimes we write one big story that is a couple pages long. We have written stories based on the book Liberation of Gabriel King, we wrote a fictional narrative, and a story based on us. We usually have 12 minutes to write a story when we have a prompt.
Here is how we do WEX in our classroom (click on the videos to see it for yourself!): http://psolarz.weebly.com/wex---writers-express.html