Start the same way you do with the taller square boxes.... I wrote it a few days ago.
This is where it starts to change. Add one more fold to this step.Unfold your second fold and take the flat side and fold it up to the line you just made.
You now have a lot more lines on your square when it is unfolded.
Your lines are going to be the same.
Fold the tips to the center
Fold that second flap down so your side walls are 1/2 as tall.
As with the tall boxes make the bottom piece about 1 cm smaller than the top.
I am loving the mixture of a Short top and a tall bottom box.