I was just thinkin about your apartment building

Is that a flat (accessible) roof or a pitched roof?

If u can access the roof, full southern facing, & can work-out the drainage details (by

diverting run-off into the spouting or into a drip line that feeds back into the garden ~~

over my head design-wise ~~ or into peripheral potted plants or something…or just let it

puddle-up & dry in the sun for that matter) then  you might be able to  lay-out  a  laudable

( …or is it  laudanum tincture that has  drained a parallel me of my olfactory senses again?)

4X8 raised bed.  The poor sun exposure of the location you have worked-out is a sorrow

to me…because every good garden I’ve worked had southern exposure.  Although my

grandma grew  grapefruit-sized tomatoes  in partial sun but she was like some kind of

 gypsy sage  who kept all the incantations of her miracles to herself; only sharing the

desired effects & holding ‘er mistakes & sloppier slights of hand close to ‘er vest.

can’t help the lyrical content