Hand out one piece of paper per row. I usually use scrap paper. Keep the rows roughly equal.
Use the powerpoint to explain the rules. You will show a story starter on the board. The student at the head of each row writes a sentences then passes the paper back, the next student writes a sentences and passes back and so on. If they finish before the time is up, bring the paper to the front and keep going. There is no need to move the desks.
I often remind them that the story does not have to be logical. For example, 'an old woman finds a giant peach in the river' could be followed by 'she throws it back in' or 'she plays soccer with it' or 'she makes a giant peach parfait' etc.
Give students some time to write your chosen starter sentence and go over the meaning if you think it is necessary. You can use one of the prompts I made, or make some of your own. If you like, you can make a sentence to practise a new grammar point.
Start the timer for 5 minutes, helping out any students that are really struggling to think of a sentence. If the timer runs out, give any students who have not written anything some time to finish.
Ask students to read out what they wrote. It may be an opportunity to practise a grammar point they are struggling with, or simply to laugh at everyone's funny stories!