How to Make an Origami Square Base

Valley fold in half both ways, and unfold. Fold the square into a rectangle and unfold. Then fold the square into a rectangle the other way.

Mountain fold (fold Behind) in half diagonally both ways, and unfold. (Fold the square into a triangle.)

Hold the paper at two corners, and bring the corners together.

Press the other two corners into the middle as well, from the outside. Basically bring all the corners together.

Make sure it looks like this. If it does, you've made a square base!