MOTM

Duh!

If I provide 90 degree bends in the long rails, the I suspect a "wood wedge"
(actually, a complimentary pair!) on the top and bottom insides could 'tilt'
the rails to give an overall slope to the *panels*.

In fact (Mark T., help me out!) a planer with a 10 degree offset could be
used to angle the *inside* surfaces of the top and bottom wood pieces
so that a 90 degree bracket 'tilts' perfectly!

You wouldn't need to plane off but ~1.5 inches back from the front edges:
just enough to
give the slope. I'm thinking 5/8" birch plywood here.

Thoughts?

Paul S.