My calculations - hopefully correct.
Cut 6" strip from 'shadow' fabric
Cut 2" strip from background fabric.
Sew together lengthwise, then cut into 1.5" units.(or your chosen width)
Sew one to the long side of the 'stamp', then another to the bottom side.
Make as many as required.
Join these blocks with sashing
[ATTACH=CONFIG]609676[/ATTACH]