Oh I understand that. I did it too on a few blocks before I realized when they say 4 or 6 inch blocks they just automatically think you know to allow 1/4" on all sides for seam allowances. So as you placed your strips, the outside strips needed to be 1/4" wider, EACH, so when you sew them you would have the correct size.
So when you are shooting for 1.5" strips you need to make them 2" to start with because as you sew them together they shrink to 1.5". Does that make sense?
NEXT.....
Blessings, Ruth