Not much to say here. You basically can build whatever you want into the pinball machine to guide the ball how you like.
Requirements are that you have your kart upgraded (I have it maxed out in the video, but lower may also works), you can then just fly out of the interiors (seems they don't have fully enclosed collision) which are located in the same world, far away to the west outside the skydome.
The pinball machine is just like a huge interior you can fly into and then build in there.
Hanna's grocery store works best for this, as it's very close to the pinball interior, so you don't need to fly very long to get there.

Note: The parts you build don't move with the flippers when placed on top of them