step 5 is not self-explanatory, because you do not see one mountain-foldnecessary - it is hidden under the flap and: it is not indicated in any way in the diagram ... (do not be alarmed by some "wrong" creases in my pictures: they are the results of my experiments to get the result

; and it is of course two mountain folds, on both sides of the flap ...)
you see this mountain-fold in the picture above: it is bisecting the angle. preacrease this mountain-fold, then you do have the reference-points for the valley-fold shown in the diagram, and the reference-points for the mountain-folds shown in the diagram.
now push down at the point of the valley-fold. the right point will move upwards, and with the three mountain-folds (two of them are shown in the diagram, we have produced the third one) you create some kind of petal-fold - it is not a petal-fold in the "traditional way"
the result:
