Here is what I figured out for the blocks on that over/under quilt pattern. Hmm, I can't upload the diagram.
The blocks are 6 inches finished with block A made up of 3 rows: 1 and 3 are colored 2 1/2 x 6 1/2 inch strips
and row 2 is three 2 1/2 inch blocks with the center one white.
Block B is also 3 rows: first row is 4 1/2 inch colored strip and one 2 1/2 inch HST
second row is one 2 1/2 inch colored square + 2 1/2 x 4 1/2 white strip
third row is one HST + 2 1/2 x 4 1/2 white strip
They are grouped as: B,AA,BB,AA,BB,AA,B both horizontally and vertically so it finished as 72 x72 inches plus the borders.
I hope this all makes sense.