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
The Re-poll has arrived, many pointed out with the last poll we ran that the update would change a lot of the out of bounds clips and those should be re-done. Since then some different clips have been found and others have changed, even a new universal clip was found so we believe it's time to redo