I saw a diagram where someone set up a "lean-to" with just a few slats directly north and above a plant. That way, the shadow only fell on the plants around Noon.
The slats were spaced apart so that they gave around 50% shade.
You could put up the poles and position the slats just before the hottest opart of the day, and check it a few hours later to see if you were creating shade in the right spots at the right times.
But it might be difficult to make this look good!
