I remember it featured a vertical room with conveyors connected to it and at the end of those conveyors there were rooms with different NPCs you could slaughter in different ways. The conveyors would then transport the gibs all to the vertical room.
I've already looked through GameBanana, Snarkpit and THWL's vault without success of finding it again and searching without having the slightest hint of what the name could be didn't get me far, looking for things like "slaughter" or "test chamber" just leads me to either Scientist Slaughterhouse or different iterations of the actual black mesa test chamber. I did find a similiar styled map while going through the vault, though: The Crab Lab v2.0
And I found it, called blood inside of a map collection from Richman, the guy who did Hazardous Course 2