To make your own blackboard, just buy some blackboard paint, pick a wall and paint about 3 layers of paint on... It's that easy. Paint is water based and works really well.
Some judges have silly rules. I got nothing for the best collection of herbs, because a couple of mine were in flower, and only second for mulberries when I was the only one in the category because the jar wasn't full. I don't make these things to sit on a shelf and look pretty, I make them to eat! And with the herbs, the one they pointed out was Borage of which I only eat the flower... arghh. Someone needs to write a guidebook for entering things at the show...
Enough of my rant. I also got three highly commendeds for photos I entered, and I am going to use all the photos I printed as gifts to people through the year.