Apparently, this is something truly Belgian: kids (or their mother, aunt, grandma) create paper flowers and sell them on the beach. The exchange money are handfuls of shellls. The first paper flowers would have been sold in the 1920s.
I fondly remember the days when my sister and I used to make paper flowers. Whenever there was a rainy afternoon, our mother, cousin Lea (who always came with us as sort of au-pair) and we two kids sat at the large kitchen table and began to make flowers. What you needed were green sticks (for the stems) and of course, paper. You could find it in many colors, but we only took those which also existed in nature. And I must say, we made quite beautiful flowers (double-layered and all). Then when you could go to the beach and set up your stall, you had to be careful not to be cheated and you also had to know the value of your ware. Our flowers were expensive, because they were much in demand. We sold them for at least 5 or 6 handful of shells (and took care that the other kid did not mix sand between the shells).
I suppose many kids learned the art of trade on the Flemish beaches, from De Panne to Knokke-Heist!
Btw, are there any other who know this custom?