Combine baking soda and cornstarch in a saucepan.

Add water to the saucepan.

Cook over medium heat, stirring constantly.

Continue stirring until the mixture thickens to the consistency of moist mashed potatoes.

Remove from heat and turn the mixture out onto a plate.

Cover the plate with a damp cloth.

Let the mixture cool until it is cool enough to handle.

Roll out the mixture to a 1/4-inch thickness.

Use cookie cutters to cut out shapes.

Press a hole near the top of each ornament.

Place ornaments on a flat surface to dry.

Let the ornaments harden overnight.

Paint and decorate the dried ornaments.

Protect the decorations with a shiny glaze.