Perhaps the most important step in this effect is the cropping choice. The fragment that you crop out shouldn't have any "dead space" and doesn't need to have any symmetry to it; that comes from the subsequent processing. Here is the sequence for another one I did:
Once you have cropped it to your liking, apply the rotates & flips (or run the script) to get the 4-fold symmetry.
After that duplicate the layer and find a blend mode that you like.