To sew the block's side units, sew a Color 4 Quarter Square
Triangle to the Straight short end of a Color 2 trapezoid. Press seam
towards the trap. Add a Color 4 Half Square Triangle to the top edge
of the trap, pressing seam towards the triangle. Now sew a Color 1
Half Square Triangle to the pieced triangle you just made, and press
the seam towards the Color 1 triangle. Make four units like this.
These should measure 3-1/2"...