A fluid coatlet; a jersey cotton fabric.  Cross slits were cut  as the button hole.

The material from right front is drawn through.

Pulled through further and then turned back and drawn through again to secure more firmly.

A simple fastening;  the ends remind me of the wings of a dove.

Might as well mention the cuff-less cuffs while I am here.  

I did not want to sew on cuffs to narrow the sleeves as this would compromise the integrity of the simplicity and flow of the design so I rolled up the sleeves two or three folds, took a substantial hair elastic ….

… turned the sleeve inside out,  zapped the material at the seam pony-tail style, turned the sleeve right side out and tucked the tail inside.

Here is what it looks like when being worn.

It's a comfortable sleeve ending,  holds its stance if pushed up on the arm for coolness or style,  can be adjusted to make the cuff wider or narrower.  You can also use a colourful scrunchy without turning the sleeve inside out and this results in a funky external cuff LINK.