This glitch lets you crawl while you have no block underneath you
steps:
step 1: create a 5 block high box with a ceiling
step 2: create a 1x1 hole that meets with the ceiling
step 3: make the crawl contraption which is made in the steps of this video: https://drive.google.com/open?id=17iyyUNE4TL0kf3usRvw53jEDkYnc0N4Z
step 4: connect the crawl contraption with that hole
step 5: get enchanted golden apples
step 6: put shulker boxes in the box
step 7: use the crawl contraption to get in that hole (stay in it)
step 8: make it so you can't get out of the box but stay in the hole
step 9: get in survival and wait until the shulkers hit you
step 10: eat a enchanted golden apple and then get in the box
You should be crawling while only air is below you.
if you are not then watch this video to get a better understanding and maybe fix it.
video: https://drive.google.com/open?id=1auGuGBTm7gANZrNRz9KqtVp2yHv6xG5e
and for another one with levatation: https://drive.google.com/open?id=1CkF1WLQWhiWcTKd1ItFMrt3qrvuwuUfn