Catch and evolve a male Numel. Camerupt learns Rock Slide at Level 33.
Catch a female Spinda and breed it with the Camerupt until you get a male baby. The baby Spinda will have Rock Slide.
Breed the male Spinda with a female member of the Machop line. The baby will be a Machop with Rock Slide.
Source: Bulbapedia
