Look at these river rocks I found. They're heart shaped. And I carved them, and I'm going to give them to Jon for Valentines Day. Ah ha! Gotcha! They're made out of air drying clay! Want to know how to make them? They're perfect for the caveman in your life. The only skills you need are the ability to squish clay and to operate a toothpick.
First, get a lump of air drying clay from the craft store.
Form it into a heart shape.
Then write your message into the wet clay with a toothpick. First just barely draw it in there lightly. Then press down harder.
After you carve it in there nice and deep, run the wet clay heart under water to smooth out the bumps around the letters.
Now let it dry completely. To make it look like a river rock, you'll need white craft paint, black craft paint, and a stiff paint brush. Dab up a little black and a little white paint onto the brush, and start stippling (stabbing?) it onto the rock. Don't brush. Just pounce.
Keep picking up white paint and black paint and stipple stipple stipple.
Make sure you get down into the words you carved.
Paint the top, let it dry, then paint the bottom.
Voila. Little faux carved rocks.
Perfect for the man who has everything or for the man who has very little in the material sense so you can't really go spending his money on stuff for him except for when his underwear finally falls apart.