Get a stiff cardboard (I recycle a mushroom packing box 0r cut from a lid will do too!)
and cut a shape like the picture - you can be creative after this tutorial...

The cardboard have to be stiff and flexible enough for
a nice curve bend when you press it this way!

Cut 3 pieces of the cardboard - exactly the same shape and size.

Wrap a piece of rag / clothes..felt with be a good choice
but I don't have any and it's very expensive here..
You make wrap it with double side tape, glue gun, anything
that is friendly to handle.

This is the front look like after gluing.

I cover the raw edge at inside with duck-tape..
You may sew another piece of clothes for the lining...
but I'm not good in sewing..so, this is my best option..

After done above step with the all 3 pieces...
Take two of them and sew up the side..
the inner side is facing each other..

You will get a small pocket like this.. continue connect
the other piece with one line of stitch too.
Remember not to close up the whole thing...

After you done with the third piece, you will
find a nice triangle piece of purse that will open
when you press on both ends..
and the 'Pop Open' purse is done...

This part I add up myself...I think it will be cuter if
I spice up a bit and
change the purse into
..

A MOUSE!

I'm so addicted after my first one so I did some more...

A fish... and...somemore...

This one a bit crazy.... Have fun!