How to determine the right K points for the band structure of a slab?

[Alford]

I am trying to compare the band structure of a slab and the bulk phase, just like the example on the VASP wiki( https://www.vasp.at/wiki/index.php/Ni_1 ... dstructure). In the example of VASP, it calculates the band structure of the slab of Ni metal.
A slab is basically a crystal that has a new kind of symmetry, but the example doesn't generate K-points from the slab, it uses the K points extracted from the Brillouin zone of the bulk primitive cell. I am not sure if this is appropriate.
And I should follow the way in the example, why should I choose K points from the one facet of the Brillouin Zone of bulk phase?