http://classicalpoets.org/how-to-write-a-sestina-with-examples/
How to Write a Sestina (with Examples and Diagrams)
The sestina originated among the troubadours of medieval France’s Provence region, and the modern thirty-nine line form is attributed to one of these traveling poet entertainers of the twelfth century, Arnaut Daniel. Daniel’s sestina form was admired by Dante Alighieri, who introduced it to Italian poetry as well.
The sestina is one of the more challenging forms of the era, and perhaps that is one reason it is also a very fulfilling form to craft a poem in – especially when it comes together well. Like many French forms, like the villanelle and the triolet, the sestina is very strictly patterned. Unlike these other forms however, the sestina in its original form was not written using rhymes.
Instead it uses a set of six ending-words in six different patterns of six-line stanzas (sestets), followed by a three-line envoi which uses all six of these refrained words. This gives the poem its thirty-nine lines. The sestina is a metered form, and as long as the pattern is maintained any meter may be employed; in the English language, iambic pentameter is the most common meter chosen.
