In my Casita
, the factory used angle aluminum brackets screwed to the window frame. Then they simply placed the blind housing on the bracket and screwed from the bottom into the housing. I see no reason why this couldn't be accomplished for your window coverings.
Just make the wood slat a bit wider, place it on top of the brackets and screw from the bottom of the slat. If you needed the wood to be higher, just flip the bracket.