Start with a small tree or branch of a tree about 2 to 3 inches in diameter. Cut the tree into 3/4 inch thick cookies, let the wood dry, sand it smooth, and apply a couple coats of varnish. This makes a nice cross-section of the tree for use by school teachers. They are teaching students about the annual growth rings and how a tree grows.
The Minnesota Department of Natural Resources has a web-site page with variouis things one can volunteer for. I choose this as I like to work with wood and find the patterns in wood very interesting.
In this one, beside the variation in the annual growth rings, you can see two small branches that are buried in the wood.
After I make them, I apply a small label as to the species of tree and where it was harvested. Then I send the cookies to a lady at the DNR office who distributes them to the various school teachers around the state.