Foundation of Origami ConVase - The Square Base

All my ConVases are based on the common Origami Square Base.

For the benefits of beginners in origami, I have decided to demostrate it's preparatory steps here. There are many other ways of achieving the same thing.

Step 1

Use a square paper, pre-crease four straight lines in accordance with the following picture.  Fold in the direction towards covering up the visible lines. This will make subsequent folding more smooth and natural.

Step 2
Fold along the diagonal line, forming a triangle. 

Step 3

Separate the two layers of paper from the right, bringing the pre-creased line towards the left, at the same time bring the right corner to the top, forming a square naturally.

Step 4

Turn the paper over, repeat the above steps. 

That completes the "Origami Square Base". 

You should have four tips at the open-end at the top. The pointed tip at the bottom is the center of the square paper.   

I shall refer to the vertical line as the Vertical Central Line, VCL, and the horizontal digonal line - the Horizontal Central Line, HCL. 
This is just for easy reference  to facilitate easy instructions; you need not actually draw them as they are already formed when you pre-creased the paper.