Building Downwards? Or Bridges?

Multiple times I've found myself needing to provide myself or my pals with consistent paths and access to lower elevations or across gaps. While I could climb back up or glide across, my first instinct is to build a downward staircase or a bridge, which more often than not doesn't work.

I imagine workarounds include placing foundations on the lower elevation and building upwards with alternating stairs and walls, or placing one a wall's height down a cliff or in a river, then placing a wall and making a bridge from roof pieces, but I could also not be trying to place things correctly.

Any insight is appreciated.

Separate, quick topic: do your pals also break when trying to navigate multi-story structures?