The attached PowerPoint file contains the directions for finding the building instructions for the tribot used in the LEGO EV3-G animations and CMU programming tutorials.
Alternatively, here are links to the LEGO Education website building instructions for the Driving Base with Medium Motor Arm Attachment:
https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-rem-driving-base-79bebfc16bd491186ea9c9069842155e.pdf [1]