How was washout achieved?

[abufletcher]

Many of the thin-wing aircraft of WWI had built-in washout. How exactly was this built in? In some cases, on upper wings, the washout seems to have been accomplished just with several degrees of torsion in the aileron structure giving a bird-like feathered effect. On lower wings the washout is often harder to spot in old photos and can even make a straight wing appear to have a curved TE from the rear.

How is this washout built in? Do the outer ribs actually have a different shape from the indboard ribs? This would seem to be a nightmare from a construction standpoint.

BTW, I'm particularly interested in the washout on the Pfalz DIII.