It looks like he has planar mapped the entire mesh along the Z plane.
You can map specific faces in the Unwrap UWV modifier, you just go into selct face sub-object mode.If you want more control over scale, then use UVW Map.
Theres a couple of ways you can do it.

The cube on the left is planar mapped along the Z-axis.The cube on the right has used 'Box' mapping, one of the options in the UVW Map modifier.UVW Mapping will still require unwrapping, in order to arrange polygons so they are not overlapping(unless that is desired).
To map specific faces of a mesh, first apply an 'Edit Mesh' modifier
Then select the faces you want to map
And then apply the UVW Map modifier
Repeat the 3 steps for any further faces you wish to map.