Modular origami pyramid can be made in a few simple steps outlined below.
Glimpse of the Result:
Take a square sheet of paper.
Fold in halves horizontally, vertically and make creases. Unfold.
Make a crease at the center of the lower half of the paper as shown.
Lift the bottom and fold it to meet this crease made.
Now fold the whole model in half bringing the bottom edge to meet the top edge of the paper.
Make a cup board fold to meet the center of the model.
Make a fold as shown.
Make similar units in three more colors.
Insert one unit in the other as shown.
Similarly insert all the four units; one unit will form the base of the pyramid.