I've installed wooden shutters in our three front windows, as instructed by SWMBO. [I think there's only one factory in China where these are made, but up to twelve weeks delivery. Slow boat from China.]
They're well made and easy to install, but in my case the window rebates (probably the wrong word. Recesses?) are 'chamfered', so there are big gaps to fill or at least cover.
There are lots of ways of doing this, but thin slivers of painted wood would be nice. Say 30mm wide, 1.8m long, 3mm thick and easily trimmable.
Like wooden blind slats, but they're not quite there, too narrow and too short. Otherwise ideal. Ideas?