Here's the back of the block. The seams are pressed toward the darker fabric or the unit with fewer seams to cut down on bulk. Seams that meet are pressed in the opposite directions to help them meet correctly.
Where the half-square triangle units are sewn to the square, notice that the seam goes through the "x" where the seams of the triangles meet. This helps make the points sharp and not cut off.
You can see the difference between the stem units. Two were done with the excess fabric trimmed off and the other two were done "ala Mary Ellen Hopkins" and only the excess of the small square was trimmed, leaving the large square unit intact.
Click here to see the front of the block.