You need two pieces of fabric which you sew together on both edges of the bookmark; left and right. Before doing anything else, even stitching, neaten the edges to avoid fraying!
Be very careful....
...and sew very close to the border.
To create the final touch with fringe edge; tear off some yarn from the bottom and top of the bookmark. Neaten the fringe edge with scissors.
And here it is!!!!
My own design
MadMoose bookmark
Here you are: