If you want to use the ABCD pieces cut individually for a 9x9 "finished size unit:
A - 3-1/2 x 6-1/2
B - 3-1/2 x 3-1/2
C - 6-1/2 x 6-1//2
D- 3-1/2 x 6-1/2
Or if you want to "strip piece" to make an ABCD unit
Cut strip for A - 6-1/2 inches wide
Cut strip for B - 3-1/2 inches wide
Sew A and B strips together - cut at 3-1/2 inch intervals
Cut strip for C - 6-1/2 inches
Cut strip for D - 3-1/2 inches
Sew C and D strips together - cut at 6-12 inch intervals.
Sew the AB and CD pieces together.
This is probably the way I would assemble the unit if using yardage.
I would do the piece-by-piece assembly if I was using scraps.