We have just done our annual cleaning of the dozen nestboxes and 2 of them had been occupied by wasp nests. Some of the cells still have emerging (dead) wasps.
Our design of the box shows it is hinged for opening at the front, rather than the top. The box is thus easier to clean and inspect and the top can then be made watertight with roofing felt. Hinged roofs are a phaff to make and can now simply be nailed down.
The front hinge is just a nail at either side of the top of the front 'door'. The box is loosely hung from a large head nail via a similar size hole at the back of the box. The flange of the nail head stops the box falling, yet the box can easily be lifted off the nail for inspection or repair. The 'door' is held shut by a single protruding nail through the side, in an oversize hole for easy removal by hand.