Today I did the backyard chalkboard. I bought a 4x4 board at Home Depot for $7. It's about 1/4 inch thick. I am a total chick in a hardware store. Basically, I just wander around until I find something that I think will work! No clue what kind of wood it is, what a 4x4 piece of wood like that is used for....it was smooth, a size I thought would work and I could lift it and fit it in the Suburban. Also, at HD I finally bought the non-sanded tile grout that I had pinned for adding to any paint color to make chalkboard paint. Just in case you are like me and had never heard of such much less tried to find it in the flooring section of HD, I'm including a picture....
It was $4.98 for a box that will enable me to make enough chalkboard paint for the rest of my life. Seriously. I added 2 T. to an 8oz bottle of green paint and went to work on the board. I don't know how many coats I did, I just kept going over it until I used it all.
You could stop here. But, I found some small 1x1 accent tiles on sale while strolling thru HD, so I glued them around the edge to give it a more garden feel.
Huge hit with the kids!