You cut the repeats of the fabric into strips
When you stack the repeats, each strip is identical to the one above/below. All of the designs are in the same place. Ex: specific leaves are all in the same place, and the flowers too. So if you look at any element of the fabric, the same element repeats all the way down each stacked strip.
When you cut these stacks into pieces, each individual piece is exactly identical, which give the Kaleidoscope effect.
This is for OBW's, stack and whack and kaleidoscope quilts :D:D:D