It looks like a disappearing nine patch, and each part of the foundation nine patch looks to be six inches ... maybe a bit bigger, since ... say like seven inches? because of the 1/4" seam allowance, your 7 inches becomes 6.75" on first seam ... then you make the cuts ... mix em up and sew back together - - now block is 6.5" ... and then you join the blocks together ... now the block finishes at 6.25" ...
What a good idea of a quick, fun, fast, easy lap robe!
Good job! <wave>