To make the cookie tree: Refer to the tree template and copy its shape onto a piece of foam core. Use a paring knife to cut out tree shape and discard. Place a sheet of parchment paper on your work surface. Lay the foam board on top of the parchment paper. Use an offset spatula to spread a 1/4-inch-thick layer of tempered chocolate inside the foam template, careful to coat to the edges. Let the chocolate harden slightly, 4 to 5 minutes. The chocolate will be firm enough to cut, but it will not be hard. Lift the template away from the chocolate tree. Move this finished piece to a clean space on your work surface out of the way. Repeat the process 7 more times so you'll have 8 tree outlines.
For the support: Roll a piece of parchment paper to make a tube about 1/2-inch in diameter. Tape the paper closed. Fill the tube with tempered white chocolate to six inches. Let the chocolate harden slightly, 4 to 5 minutes. The chocolate will be firm enough to cut, but it will not be hard. Cut 3 pieces of the chocolate tube, each about 2-inches long. These will be used to support the tree when it is glued together.
To make the base: Place a sheet of parchment paper on your work surface. Use an offset spatula to spread a 1/4-inch-thick layer of tempered chocolate on the paper. This will be the base for your tree. Let the chocolate harden. You can also paint a piece of cardboard with chocolate to create the base. That will be sturdier and allow you to move it more easily.
Use the tempered chocolate to "glue" the first tree piece to the base. Join the second tree piece using the small tubes of chocolate for additional support where the tree pieces meet. Continue "gluing" the pieces together until all 8 are assembled. Let stand until the chocolate is dry.
You can decorate your tree with homemade or store-bought cookies or candy. Use the tempered chocolate to glue the decorations onto the tree. You can string popcorn or cranberries. You can glue mini candy-coated chocolate baking bits onto the tree to represent lights. Use your imagination and have fun!