Pupils collect from home all empty cereal boxes egg boxes, and any other cardboard conatiners etc.
I work in groups of max. Each group collects empty cartons etc. On the day, I use the maths lesson for the market day, I use their scheduled hour for maths. On this day their group will be responsible for selling and marketing their products. I intoduce them to the theme by encouraging them to think of things that will sell at a market, not the average every day sort of item.