1 cup cornstarch
2 cups baking soda
1-1/4 cups cold water
Combine dry ingredients in a saucepan. Gradually add water until the mixture is smooth. Heat, stirring constantly, until the mixture reaches a moist, mashed potato consistency. Turn onto a plate and cover with a damp cloth. When it is cool enough to handle, knead the dough.
Roll the dough to 1/4 inch thickness and cut shapes with cookie cutters. Dip the cutters in baking soda and shake before cutting.
If you plan to hang the decorations, pierce a hole with a hollow coffee stirrer or a soda straw before they dry. Allow the dough shapes to dry for several days at room temperature on a cooling rack. They can be painted with markers or paint.