I followed the plans to attach the whole bat box + post assembly to a fence post.
I decided to use an existing fence post. This required a ladder and some very careful sawing, so I'm not sure I'd recommend this approach! However, the end result turned out great.
Remove the cedar cap, then cut out a notch in the fence post.
After doing this, I then cut out a matching (reverse) shape in the bat box post.
Finished, attached bat box, using 4.5 inch bolts and screws.
The plans mention not being too close to nearby trees, so predators can't get to it. It's hard to tell by the picture, but the tree is about 10-15 feet away.
Nice area that hits the sun. We hope to have some bat residents soon!