It was created by first flipping the image, then erasing the empty half of the flipped layer so the boy was mirrored, no blending mode used. then that was flattened and some various transformations were applied to weird out the rendering.
Then I used a vertical flip and so forth and so on, but this is where it got interesting: I found that by using a "darker color" blend layer filled with white, and running a foreground-to-transparent radial vignette on it, and using a lightish color, I was able to completely eliminate a surround of bright yellow that was bothering me.