For anybody attempting this and trying to do it quick, I recommend you follow a speedrun, for this guide I will be referencing this speedrun by Gelly (
)
At 0:23 he does a wall clip, go up to a wall and put the block at your feet and you will clip through, I personally found the clipping to be easy, but bringing the block with you is much harder, you need to either lag the game at the exact time you're looking behind you, or jack up your mouse sensitivity in the settings in order to move faster than your refresh rate and basically glitch the block through, for the lag method you can spam your screenshot key. Personally I found it hard to follow the video in this exact spot, and what I did instead was move onto where the Blue Tree is with the 2 blue cubes, use 1 cube to open the door, then take the other cube and jump off onto the other platform, but don't place the cube, instead clip into the wall and do what I just said to bring the cube with you, it is hard and takes practice.
Here's a video guide for clipping the block:
The rest of the video is self explanatory and easy to follow.
Here's a guide made by the official speedrun.com community which has some very useful tips:
https://www.speedrun.com/manifold_garden/guide/mfbzy