I always cut UF cable vertically (like I was splitting a banana) alongside the ground wire to the desired length. Then I pull the ground wire out with pliers. Next, I score the two sections using the hollowed out half rounds where the ground was as a guide. Next, I pull the two remaining insulated conductors out with my pliers through the scored line. Last, I cut off the sheathing. Quick and easy, never any damaged insulation.