Make up simple kits from 12mm External Plywood and then the Cubs assemble them. Cutting plan for 14 boxes from a sheet of plywood and step by step instructions included.
The kits are designed for making one bird box between two cubs. You can do more or less work beforehand to make it simpler and quicker.
Hammer, Galvanized Nails, drill, saw, staple gun, galvanized staples
12mm External Plywood, Old Bicycle inner tube, cabin hooks,
Instructions in attached files