To do this glitch, you will need to jump forward one time, placing yourself close to the ledge and immediately jump forwards again as far as you can towards the ledge you want to grab on. Then, as soon as you are about to grab the ledge, attack. This will overide the grab and now allow you to freely walk around on what seems to be thin air. Do not spam attack after the second jump, you have to attack at the right time, and make sure you are very light with your controls on the first jump if you do not have a lot of room or the game will think you want to go all the way off the ledge before the second jump. It is best to give yourself as much room as possible.

Inputs can also be seen in the video if you need them!