This description from Daniel Nestor, the editor of contemporary sestinas The Incredible Sestina Anthology, offers a concise introduction to the history of the sestina and also gives a good diagram we’ll look at in the video presentation. This introduction was published on the Best American Poetry website.
https://blog.bestamericanpoetry.com/the_best_american_poetry/2013/10/introduction-to-the-incredible-sestina-anthology-by-daniel-nester.html
The chart below is from the post above. You will notice that the sestina has a pattern of end-words, or teleutons, that are repeated and appear at the end of each line.
Stanza 1: 1 2 3 4 5 6
Stanza 2: 6 1 5 2 4 3
Stanza 3: 3 6 4 1 2 5
Stanza 4: 5 3 2 6 1 4
Stanza 5: 4 5 1 3 6 2
Stanza 6: 2 4 6 5 3 1
Envoi: 2/5 4/3 6/1
In other words, a complete sestina should be 39 lines long. Many students have truly loved this form. Don’t be put off by the challenge. In another article on being a sestina editor that appears in Poets and Writers magazine, Confessions of a Sestina Editor, Daniel Nestor writes about the “love-hate” relationship many poets have with sestinas, and also give a nice history of the form if you want to know more.