To start, you will have to place a ramp followed by a wall in front.
The first one to go over and the most popular are 90s. This technique has become popular for its simplicity and effectiveness. They are used to quickly build up while turning 90 degrees in any direction which is where it got its name. To start, you will have to place a ramp followed by a wall in front. Next, place a wall either to the left or right depending on what you prefer. And finally jump and place a floor and another ramp which resets the process back at step 1. There are variations from the 90's but this is the simplest and fastest way to do them.