I just followed the instructions:
1. Trace the pattern onto plywood.
2. Cut out the shapes with a jigsaw.
3. Sand the newly cut shapes.
4. Takes them to the beach.
5. Impress them in the sand.
6. Remove the pieces and photograph the resulting depressions.
7. Dry the shapes.
8. cut a piece of wood to mount the shapes on to.
9. Undercoat the shapes and the wood backing.
10. paint the backing board white and the shapes red.
11. glue the shapes to the board.
And it totally worked!
Well, I did all that, but they never said what it was for.
I don't even know who they are.