My latest illustration trick: make complex non-Boolean combinations of shapes by overlaying simple shapes, exploding the overlay into simple regions, and unioning the regions into the shapes I want. Exploding and unioning are single clicks in Illustrator's pathfinder tool. I used two levels of this technique to make the attached diagram of a Brunnian link (https://en.wikipedia.org/wiki/Brunnian_link): once to make the shape of a single component, and again to make the over-under relation between components.