The Slip and Slider badge is for "Sliding for 2 minutes (120 seconds) "
This is cumulative and can be unlocked really quickly. The only condition is that you need to have purchased the "Slide" perk from the Nurse at the prescription counter.
Then load into a trial and sprint + crouch to slide, repeat this for 2 minutes and you have your achievement.
Also two handy things to note:
1. The in-game badge menu tracks your progress.
2. Leaving a trial after gaining progress still counts towards it.