Supply your students with squares of cardboard, craft glue, acrylic paints and some paintbrushes. The students can shape the cardboard squares any way that they would like to form the structure of their tree house, without having to actually construct the hide-away on trees. Once they have glued their structure together, let the glue completely dry and then have the students paint their tree houses using their own designs and color schemes.
Craft or popsicle sticks are simple building tools. Have the students make a square with four craft sticks by placing the first two craft sticks length-wise on a table, then laying the other two craft sticks the width of the structure at the top and bottom. The ends of the craft sticks for the width should rest on top of the ends of the craft sticks for the length, glued down with craft glue. The process of gluing down the craft sticks for the length, then the craft sticks for the width is repeated over and over until the desired height of the tree house is achieved. Students can add a roof and/or floor by simply laying craft sticks across the bottom or top of the tree house and gluing the sticks into place.
Paper allows younger children to build a tree house in any desired shape by folding the paper as desired and taping or gluing the paper together. Provide plenty of paper for the students to work with, including enough to allow for mistakes or shape changes. Provide a few models of paper tree houses that you have made for your students to consider as they build their own. The paper tree house may be painted or decorated with markers, as desired.
Small square tissue boxes are useful in making miniature tree houses with you cut off the top and turn them upside down. Assist your students in cutting out doors and windows in the box and creating a floor for the tree house with thin sheets of cardboard or paper. Once the openings in the tree houses have been created, let the students paint their tree houses as desired.