Having made some underfloor entrances (UFEs) with solid floors, I thought I’d do the same thing with my mesh floors. There wasn’t a huge amount of difference between the two types other than the need to cut the mesh back to size.
The mesh floors also had sliders for trays, that weren’t a particularly snug fit. I cut down some Correx to replace the trays and sealed the gap at the back with draught excluder, so any wind blowing underneath during the winter shouldn’t now get into the brood boxes and cool them down.