Find a spot where the sun will keep shining even as the shadows move.
Lay out your paper. Place your nature objects and/or toys on the paper.
It works best with objects that lie flat against the paper, and if you leave spaces between the objects.
If there is any wind, secure your paper if the objects are not very heavy by putting rocks on the edges.
Under the object, the paper will stay dark, while the sun lightens the surrounding paper.
The longer you leave out the paper, the stronger will be the contrast for your shapes.
There is a product called Sun Print paper that will give a stronger result in only a few minutes, but this is a homemade version.