In a medium sized pot combine the cornstarch, baking soda, and water. Stir over medium heat. After a couple of minutes, the mixture will begin to thicken.

When it looks like smooth mashed potatoes, remove the pot from the heat. Spoon the ball of dough into a bowl and cover it with a damp cloth or plastic wrap until it's cool.

When it's cool, knead it on a smooth surface (I use my silicone mat for this. I use this mat about 3 times a week while baking.) until smooth and silky. Add more cornstarch if it feels too sticky and/or sticks to the surface.

You can let the ornaments air dry over night in a warm place or you can bake them.

To bake: Preheat oven to 175 degrees F. Line baking sheet with parchment paper.

Roll out clay to ¼ inch thick on a silicone mat lightly dusted with cornstarch. Use cookie cutters to cut out shapes and add holes if you want to hang them. Transfer shapes to the prepared baking sheet.

Place them in the oven for about an hour, turning them over halfway through cooking.