Bats are a protected species, so once you hang a bat box it’s illegal to disturb it in the future – so choose where to site this with a little thought.
Contrasting oak and sapele are left rough cut on the inners so the bats have a grip to creep up, and will then happily roost in the bat box which is held forward of the wall with back supports. The supports are pre-drilled for ease of hanging, so a couple of screws drilled into a suitable wall, preferably high out out of reach of humans and animals, and your bat friendly habit is ready to be inhabited.