I picked up on Mikkel's build and for mine created a template from thin aluminium strips on a base, suitably angled. I then offered up the individual 0.25mm * 1mm PS strips pre-cut to length into the grooves. Gluing to the side strip was with limonene, anything else glues everything to the spacers as well.
In the end I found it more reliable to mount the fragile louvres onto a thin piece of black PS sheet. The louvre strips inserted first and the PS sheet glued onto the top. This being fine as I didn't need see thru for my roof vents.
The finished build, while not as good as Mikkel's can be found here
Upper Hembury Stables