This is probably obvious to most of you, but not all of this game's out of bounds tricks save time in races; in fact, relatively few of them do.
This is because of the game's use of checkpoints (you
need to pass
each checkpoint in order to pass the Finish and clear the race). The way the game handles passing a checkpoint doesn't really help things either, as you need to pass
literally under one in order for the game to register it as passed.
One thing you could do is just skim the outside of the track's walls and clear the checkpoint while remaining out of bounds. It's disappointing that you can't just drive past the co-ordinates of the checkpoint to do the same thing, but we can live.
To go out of bounds, you have to drive into a 'barrier' (either the green arrows or the red crosses) at a certain angle and point to where you will clip through it:
Also note that not all barriers can be clipped through. One reason is because it is in a spot where you can't build up enough speed to clip through it. The second (and the reason why route planning is king here) is because the barrier can't be clipped through. Some barriers actually cause you to crash when you collide with them instead of trying to push you back like normal, so watch out!
Oh, and one more thing. Something the video above doesn't show is that sometimes when you go out of bounds, "WRONG WAY" may appear on screen, causing a red barrier to spawn behind you. If you can lap the track and drive through the back of the red barrier, you will be shot forward and get a ~20MPH speed boost! If you can keep boosting for the whole race, you can keep this speed as well.
PS. I'm just AdderDee using a new account to match with my YouTube one.