To create kaleidoscopic effects in patchwork blocks, each of the fabric patches must have identical designs.
However, even though you work really hard to cut the pieces exactly the same they do not always match. Because fabric can stretch during printing or cutting, even though the mirror line on the template runs exactly down the middle of the mirror line on the fabric, it is possible that the opposite sides of the patch will not have exactly the same motif as the left side. Sometimes it is off by as much as an eighth of an inch.
So how to get that perfect kaleidoscopic effect? Simple! When pinning the pieces for sewing, line up the design printed on the fabric, not the edges of the patches. If one of the pieces is off by an eighth of an inch, then the other side will be off by the same when you sew the other side. These off-set pieces will even each other out and the designs will line up perfectly.
As indicated by the arrows, the fabric design does not match exactly on both sides.
Although the seam allowances are uneven on each seam, they will even out over the whole unit.
By matching the design and not the fabric edges, you get a perfectly matched unit.