How do I build cliffs?

[Barbamaus]

Hello,
I've been trying to use the scaffold system to build tall cliffs, but I can't seem to figure it out.

The most I can get is a 1.9m cliff, but according to the wiki it says the top is 4m (also screenshots show much taller cliffs than the ones i get).

The issue seems to be that after the first part becomes a cliff, I can't keep raising it, because when I get close it interacts with the cliff edge and no longer drops soil.

Can anyone with more experience explain to me how this works? Thanks