I used a fat quarter that was 21"x18" and cut it to be 21" x 8.5"

It will cover the scriptures just about right.

I gave myself a quarter inch hem all all sides.

And turned it over twice on the short sides.

I got so into I forgot to take more pictures.
I measured the width of the entire book that needed to be covered,
(make sure to do it when the book is closed)
and sewed flaps with the excess material on both sides.
I hot glued buttons and ribbons to it for a closure.

I wasn't in love with the original color bookmarks. I cut them off.

And added my own.