I made this example of the 39 lines because offers a different visual pattern than the one described in the resources in this post. You are repeating the six end words, which are called: teleutons.
How to Write a Sestina Sestina
Line 1, stanza 1, ends with word one
Line 2, stanza 1, ends with word two
Line 3, stanza 1, ends with word three
Line 4, stanza 1, ends with word four
Line 5, stanza 1, ends with word five
Line 6, stanza 1, ends with word six
Line 1, stanza 2, ends with word six
Line 2, stanza 2, ends with word one
Line 3, stanza 2, ends with word five
Line 4, stanza 2, ends with word two
Line 5, stanza 2, ends with word four
Line 6, stanza 2, ends with word three
Line 1, stanza 3, ends with word three
Line 2, stanza 3, ends with word six
Line 3, stanza 3, ends with word four
Line 4, stanza 3, ends with word one
Line 5, stanza 3, ends with word two
Line 6, stanza 3, ends with word five
Line 1, stanza 4, ends with word five
Line 2, stanza 4, ends with word three
Line 3, stanza 4, ends with word two
Line 4, stanza 4, ends with word six
Line 5, stanza 4, ends with word one
Line 6, stanza 4, ends with word four
Line 1, stanza 5, ends with word four
Line 2, stanza 5, ends with word five
Line 3, stanza 5, ends with word one
Line 4, stanza 5, ends with word three
Line 5, stanza 5, ends with word six
Line 6, stanza 5, ends with word two
Line 1, stanza 6, ends with word two
Line 2, stanza 6, ends with word four
Line 3, stanza 6, ends with word six
Line 4, stanza 6, ends with word five
Line 5, stanza 6, ends with word three
Line 6, stanza 6, ends with word one
Line 1 of the envoi, uses word two and ends with word five
Line 2 of the envoi, uses word four and ends with word three
Line 3 of the envoi uses word six and ends with word one