EDIT: There is an easier way of doing it with super jumps, but I didn’t know as I hadn’t got to the part where the game “teaches” you yet.
Over the elevator in chapter six. After being suspicious of this room for ages, I accidentally discovered that you can grab onto a wall despite it being covered in spikes. Countless deaths later I finally found the secret room! The video is ''edited'' so you don't have to see the hundreds of times I died trying to get there.
