All of the ones I just listed are side of the mound dwellers for me; the tops are reserved for more cherished veg like tomatoes, peppers, squash and cukes...
Onions grow srtight up no matter where you plant them, as do most of the rest. My secondary cast of characters are not finicky about growing condtions and will do with a bit more shade (from the primary cast of characters) and are all pretty short rooted so not competitive for root space...
And indeed in rbg's situation sitting on concrete it wouldn't work, but my bale gardens would...
HG