While we're on the subject of chalkboards, I love this rustic style. Granted, it's not as cheap as making your own, but I don't think the prices are too bad. This would be a great height for kiddos to access and exhibit all kinds of creative license. Another great, and even more affordable, option is the one below from Ikea.
this one in their play room and it has a white board on the other side - double the fun!
To add to the fun, try this set of chalk ink. My sister gave me these for Christmas and I love them! They are much less messy than chalk and your words come out very crisp with great color.
If you do decide to make your own, I'd love to hear how it goes and see a picture of the finished product.
Have a great week!