Click Refine -> 1m then Mean Ground then Bake

Click unbake then Extract Profile and add VIPs

Open templates, click new then

In Sections Define first side of polygon as vertical then remainder as sloping at 60˚

In Templates

For the wall section
For the sloped section

Assign sections

Calculate earthworks but ignore results in earthworks window

After baking the quantities are

and the 3D

Ignore the small black vertical lines at the base of the walls, These are an artifact caused by the noise due to the tiff being of the surface including vegetation.

If you make the bake permanent and update the terrain you can then draw sections through the slope or add other pads etc.