im bad at explaining it but basically, when you enter that first hallway, make sure you are sliding and have a fully charged core eject and just before the door, look down about 45 degrees and shoot it, you should land on the door frame of the door behind you and you uncrouch. look for tutorials on youtube for a practical demonstration idk
when you enter the first hallway open the door at the end of it because that unloads the room behind you allowing for the clip, then you just need to dive at the door frame in any way(core eject,just a regular dive etc) and make sure not the open the door because that will load the previous room back in
Edit: using the core eject is the most constistent for me
If you have not seen ULTRAKILL is finally having a speedrunner competition for real money!!! It starts in about four hours from the time I am making this news post, in fact its probably already started when you are reading this so click the challenges widget on the right and read up on the rules and
