It wasn't that hard. It honestly took me twice as long to create the main wall than the crawl space.
Steps to creation (helpful for new people):
1. Spawn two 1x1 boxes.
2. Place them along a wall you created or a wall in the level. Make sure you put some distance between the two boxes so your plank will be straight!
3. Spawn two 1x5 planks.
4. Rotate one of the planks so top and bottom are horizontal with the ground. Push against the wall ontop of the two blocks. Drop it and freeze it when it is flat against the blocks and the wall.
5. Rotate the other plank so the top and bottom are horizontal and drop infront of the two 1x1 boxes. Push against the plank so it is flat against the two blocks.
6. Unfreeze the two blocks and move them out of the way. Then, carefully unfreeze the bottom plank (the wall) and move it slowly towards the upper plank. When you think you can crawl through it -- test it
FIRST POST HAS EXAMPLE DEMO