I thought I was going to be clever and cut each strip 4.5'', then just keep matching at the point and then trim the edges... But of course only the first strip should be 4.5 (same as the starting square),
the rest have to be 4.5+2.5 (7) Do'h!
Okay! Final calculations. Might still be wrong, but they look right now. (and I have twice the amount of strips cut that I need)
First strip to attach to the left of the white square (1pc):
All long strips, to attach on the right side (4pcs):
All other short strips (3pcs):
The first strip is obvious, as the square is 4.5
The second strip needs to cover 4.5+2.5 minus seam allowance (0.25*2) = 6.5
The other strips don't need to cover the previous all the way, because of the cut-off. You can also see in the picture that they're shorter on the left than on the right. (the braid isn't centered, because then the starting white wouldn't be square) So all long strips can be the same size, and since the second strip trims the square a little, the last three short ones can be smaller than the first.
So for the rest of the short ones you'll have 4.5 again, minus seam allowance (0.25*2) = 4