Any idea how this horror fake person effect was created?

Hi there, I’m trying to recreate an effect akin to the monster from this video https://www.youtube.com/watch?v=pzV2MB7MmWw

I’ve already recorded the masculine and feminine lines, but i cant seem to chop/repeat the audio segments in a way that gives it that ‘uncanny’ fleshy stutter and layering. Anybody have any ideas?