My answer is that I wouldn't. Plantuml doesn't support that kind of diagram or the level of layout control you need.
In particular it can't have boxes touching each other. But also "container" shapes (rectangles that contain other rectangles) lack the full set of style options. And then there's the age old problem of trying to get arrows to route how you want them, and getting boxes to stack vertically symmetrically.
That said, here's an 'attempt':
If @plantuml are watching - the biggest problem I hit was that container rectangles don't support style attributes "MinimumWidth" or "HorizontalAlignment right". Also, I wasn't sure if there was a padding attribute I could use to get the boxes to abut one another - I tried a few padding/margin settings in root, etc but gave up.
