I decided I should try sewing clutch. So here is my first :)
I cut the desired shape and size and took the green zipper.
I secured zipper with pins and sewed it on the leather on both sides like this :After I finished that I turned it on the wrong side and sewed the left and right side.
I turned it back on the right side and my clutch is done :)
(My clutch is quite soft, if you want it to be firmer paste felt or any stronger material)