To mix up the dough, you'll need:
1/2 cup salt
1/2 cup all purpose flour
1/4 cup water
Mix all of this up in a bowl...
Then when you get a nice ball of dough...
...plop it on the counter and knead...and knead...and knead...
The longer you knead, the smoother the texture of your finished product will be. Trust me, the first one of these we tried was so ugly, it ended up in the garbage.
Place a piece of parchment paper on a cookie sheet and roll out your dough until it's about 1/4" thick. (During the first attempt, I learned that a six year old's hand is a bit large to transfer, so the second time, we just went ahead and rolled the dough on the cookie sheet. I also learned that the thicker the dough, the more it will crack when baked. Thinner is better!)
Now, track down your kids, who have undoubtedly gotten into some sort of mischief while you were busy with all that kneading, and have them put their handprints in the dough.
Then cut around the print with a knife, leaving a border. If you want to hang this later, make a hole using a straw.
Bake at 175 degrees for about 4 hours. Once it's nice and dried out, just paint, seal, and hang!