How to "???? the ????" 25 times in Disc Room?

The only locked room that I cannot figure out has been the one in the top which is unlocked by the challenge "???? the ???? (0/25)" in the room Safety First. The other challenge similar to this was one that involved feeding clones to mouths in the living section, but once I figured that part out I just did it over and over again until it worked. This is the last room that I can't figure out and I have only been able to find one guide on this game. What's the secret?

Use the mirror ability to eliminate the bottom row and the first and last square in row 4, then the top row and the first and last square in row 2.