Pour the flour, salt, and water into a big mixing bowl. Stir with a spoon until you can't anymore.
Use your hands and knead the dough so all the ingredients get combined. This could take a few minutes.
Use a rolling pin and roll the dough out on parchment paper until it's about half an inch thick (or less if you prefer thinner/lighter ornaments).
Get out your cookie cutters or have the kids stick their hand/foot/finger into the dough to make a print. If you're making salt dough ornaments, use the end of a pencil or straw and poke a hole at the top for the ribbon later!
Lay a sheet of parchment paper on a cookie sheet and line the cut ornaments up, leaving at least 2 inches between each other.
Bake for 2 ½-3 hours until they are hard to touch (with an oven mit!) Depending on thickness they could take up to 3 ½-4 hours total.
Let cool and then have the kids paint them with acrylic paints.
Notes
If you want the ornament to have glitter, add it when the acrylic paint is wet! Optional: Seal with mod podge or a clear coat spray paint finish to preserve it. NOTE: If you have dogs at home, hang the salt dough ornaments at the top of the tree because they can die if they eat them.