How to make bookmarks for Arbor Day slogans?

Boil the leaves in alkali-added water, take them out and soak them in cold water. Then use a small brush, or a toothbrush, to gently brush off the leaf mesophyll, and you will have a leaf vein specimen.

For leaf specimens, just put the leaves into a book, put something thick on top, and press them overnight, then change the pages and press them again. To put it bluntly, it means letting the pages absorb the moisture from the leaves. Put the leaves in a thick book and press them for a few days, wait until the water dries, then take them out and seal them in plastic.