Tape, what tape? You must be seeing things
I like the ones under the window too. I had to cut the gap down to 2", 3" was too much under the sill, it made the square too small. I noticed some people don't add the squares when the windows are as big as mine in some online pics, but I like it better with it under there.
The other 2 walls will be
much easier, each wall will have 5 equal sized squares, on the wall in the pics, only 2 of these squares were the same, even one window was 1/8" wider than the other (yeah yeah, I'm that picky
)