You can use and old heavy book (ask permission first)
to press small plants, flowers of leaves. Just put what you want to
press inside the book and close it. Leave it there for a few weeks.
Or you can make a fancy press:
Start with two equal size pieces
of plywood (or recycled boards) as the top and bottom of your press.
With the two boards atop each other, ask a parent to drill a hole
through each corner. Thread bolts through the holes and use flat washers
and wing nuts to tighten your new flower press. Once you've collected
flowers to press, put them between pieces of paper (in yellow on our
diagram) and place layers of cardboard above and below. Let them dry
4-6 weeks.