They are, of course, incredibly simple to use.
You play with them:
And when you're done you wipe them off with a damp dish towel--
--so that they're ready for their next incarnation as pony flower garden, or pony hay maze, or pony candy land, or whatever further pony expedition you've thought up next.
My chalkboard building block tutorial is over at Crafting a Green World, and if it wasn't raining today, I'd be painting more right now! As it is, I'm seriously considering taking over the living room floor for the noble cause of multiple chalkboard building block constructions.