Collect flat plants, or other objects, to arrange. Spend time deciding on the design.
When ready with the design, take the sun print paper from its packaging and quickly move the arrangement onto it. If possible lay a piece of plexi over to make them very flat and to stop them from blowing away.
Wait until the paper turns from blue to almost white.
Take off the plants and immerse the paper in a tray of water. Wait until it turns back to blue, then remove from the water.
Dry the paper.
The sun exposes the parts of the paper that are not in the shadow of the plants.
The water fixes the design.