Kinda surprised its not here already but here it is.
You need a guest to perform this. Have the guest (or you) lie on the ground and start crawling at an angle towards the STRAIGHT and FLAT wall. Have whoever isn't on the ground walk towards the wall at a similar angle facing the prone player. Keep holding the directions and you will rise fairly quickly. You can have someone else piggyback on the guy whose standing by walking behind him.



There are hundreds of spots you can do this.