I received this link request and thought I would pass the site on to you.
Terry Taube -Natural Impressions:
http://www.terrytaube.com/
Terry is from Hawaii
Students could do this on a smaller scale - casting sheets of paper
over natural forms - then trimming away the excess. You could also
make plaster molds from shells, leaves, etc. and press pulp into the
molds.
There is a description of Terry's process on his site.
I will be adding this link to my page on paper arts.