Mix the ingredients together in a large bowl using a wooden spoon. When it becomes too stiff to stir, use clean hands to bring the dough together.
NOTE: If the dough is too wet and sticky, knead in a little more flour, about 1 tablespoon at a time. If it's too stiff, add a little more water, about 1 tablespoon at a time. There is a big range in the way different flours absorb liquid, so there is a normal range of variation here. It should be easy to work with—soft and not too stiff and not excessively sticky.
Knead a few times until the dough is uniform and soft, about 3-5 minutes.
Divide dough into 2 or 4 sections and roll out to about 1/4-1/2 inch thick between two sheets of parchment paper. This will help prevent sticking.
Cut out with cookie cutters. Transfer shapes to a parchment-lined baking sheet.
Repeat rolling and cutting out shapes to use up the dough.
Preheat oven to 250 degrees F.
Do a 4-5-inch circle and press in a child's handprint if desired.
Use a paper lollipop stick or a skewer to make a hole to hang as an ornament.
If making ornaments, bake for 90 minutes to 2 hours; if baking handprints, bake for 2-3 hours. Continue baking both ornaments and handprints as needed until they are until just firm to the touch, checking every 20 minutes. (It's not a problem if yours take longer than the initial baking time—it varies based on thickness and size...which will likely vary if you are baking these with kids!) They do not need to be rock hard, but should not feel squishy. Handprints will likely take longer than smaller ornaments and may take closer to 4 hours.
Remove from oven, let cool, and paint if desired with acrylic or washable tempera paint.
Once paint is completely dry, seal with Mod Podge if desired.