This fold is very similar to the regular Petal Fold it’s just performed on a somewhat different shape. You’ll see this variation a lot in diagrams.
2) Fold both sides into the center along the red lines.
3) Crease well and then unfold.
4) Try to make a Valley Fold along that horizontal red line.
5) Lift up like the regular Petal Fold folding against that horizontal crease you just made.
6) …push down following the existing creases.
7) The completed Petal Fold Variation.