Hes saying to buy rotors that are already cross-drilled, dont do it yourself as 9 times out of 10, you'd be damaging/weakening the rotor instead.

To summarise for you,
Best application for daily driven is BLANK rotors.
Best applciation for the occasional track day is SLOTTED rotors.

That said, running slotted for daily is ok too... but steer clear from cross-drilled rotors for daily use.