Fold the top-left corner down and the bottom-right corner up to create diagonal edges.
: On the top layer, fold the two bottom corners up to the top peak of the triangle. Flip the paper and repeat on the other side to form a diamond shape. How to Make a Paper Cube Using Origami
: Flip the paper over and fold it in half horizontally, then unfold it. Fold the top-left corner down and the bottom-right