3d object makes a 2d trail on ground? (another object)

Play at 8:10 https://www.youtube.com/watch?v=Iv7A8TzreY4&list=PLPV2KyIb3jR5QFsefuO2RlAgWEz6EvVi6∈dex=10

Followed this tutorial and had a great time. now i want the cube to make a trail on the ground , tried to use trailrender but it came out higher then the edge of the cube, and in didnt follow the edge, he followed the "center" of the cube, would be happy to get some help :) Thanks!

Added A video showing the trail right now https://www.loom.com/share/c5a159813590423dbf4619e034527452