Yes, the bees don't seem to mind the shape of the hole as long as it has a light blocking back to it. The holes on commercial trays go all the way through and they use a tightly fitted cardboard backing. Some one smarter than me determined that the square holes need more mud to seal and so make the bees work just a little bit harder than those bees using round holes. But yes square holes will work just fine.
Yes, the bees don't seem to mind the shape of the hole as long as it has a light blocking back to it. The holes on commercial trays go all the way through and they use a tightly fitted cardboard backing. Some one smarter than me determined that the square holes need more mud to seal and so make the bees work just a little bit harder than those bees using round holes. But yes square holes will work just fine.
Thanks. I have some offcuts that could be pressed between two panels, but still keep the idea of your design.