Sorry, thought you were asking about the other.
But there's some similarities. When building walls atop (or jutting out from) walls, you just need to keep in mind what helps what and what blocks what.
Take the example side-profile:
.....?!!!!!!!!!?.
...?!!+++++++++?.
.?!!+++++++++++?.
!!++++++##++#++!!
++++++####++#++++
++++######+##++++
#################
The +s, as you build them, create a walkable surface above them, and the !s and ?s don't impede the walking/building on the wall-top behind.
However you go about the walls (without other urgency) I would start by just building the walls on the lowest ground elevations, the access to build those is from the ground. Then the natural rises of ground level provide the construction access to that lowest level of war. Pick a wall-top in the middle of any such stretches (or between any ends and any mid-point stairway/ramp accesses you are building) and set a single (or pair) of walls to build, access to be along from the nearby terrain (or temporary/permanent built access).
Once you have those built, set up the next adjacent walls, either side. Once they're built, the next. Terrain-flush (not wall-top) walls at that level can be set up without such ordering (but because of the LIFO, do that first and then the rest that you designate gets priority and these take up the slack in your micromanaged job queue), but leave off at least one (might need more, for some local geologies) plateau-edge walls where access to the final wall-top walls need building from, to be the last gap to fill.
(Assuming you aren't just lining the inner side of the wall with gangways (floors, or perhaps 1xN bridges) for permanent or temporary access.)
Once you have wall-tops from which the overhangs will hang (you don't want to fill those actual tiles with wall), put a ramp on the wall-top behind the ?-marked overhang (or a stairway, anywhere, but especially where it is a multi-z step change, like that to the RHS of the diagram, unless you want to modify it to a series of ramps across the cruck of that angle), and access is maintained for all further management of such constructions, so long as you have riser stairwells at
some part of your site once the construction rises above any or all local terrain maxima.
Or, just build as much wall as you can, topping it off at an arbitrary level of your choosing, then go around digging channels around the outside where the wall needs to be higher than you actually built it.
I like doing this anyway (a dry moat and drawbridges across it at strategic spots makes for additional access/egress control in various useful ways), but you then need to make sure that you 'reserve' the underground just below the "just outside the wall" surface, so you don't have to reseal a tunnel out to your prime subsurface farms, or whatever.
Again, loads of words, and I could diagramise it further, but I'm aware I may yet be misconstruing your need. And in a few hours I'll be back home and not be forced to tap this out whilst walking between the places I'm visiting today, narrowly missing walking into both complete strangers and half-completed street furniture...
ETA: I just gave a wave of thanks to a car that actually stopped to let me across a zebra-crossing. Which, given that it was a police car not otherwise in a rush, it was pretty much obliged to do. I do hope they got the nice feeling out of my gesture of gratitude, anyway. Nothing to do with walls, but follows up on what I just closed on. Never mind.