We had a sheet of timber in the sheet left over from something. I love being able to use left over bibs and bobs so we bought some blackboard paint and used it to add a large blackboard to the children's cubby house.
sans blackboard, the cubby sitting in the orchard.
They seem to be enjoying it.
I was going to put the blackboard inside the cubby, but by putting it on the verandah I can see what they are drawing from the front yard which is nice.