If I want to include a DOI for a book chapter in my works-cited-list entry, where should I insert it?

If you are citing a chapter of a book from a novel or monograph, create an entry for the book as a whole and list the book’s DOI in the “Location” slot, since in MLA style, chapters from these types of works are not cited individually. 

If you wish to include a DOI for a chapter in an anthology, include it in the “Location” slot:

Lewalski, Barbara K. “Paradise Lost, the Bible, and Biblical Epic.” The Oxford Handbook of the Bible in Early Modern England, c.1530-1700, edited by Kevin Killeen et al., Oxford UP, Nov. 2015. Oxford Handbooks Online, https://doi.org/10.1093/oxfordhb/9780199686971.013.34.

If the chapter has page numbers and is contained in another work, include the page numbers in the “Location” slot of the first container:

Bould, Mark. “Speculative Fiction.” The Cambridge Companion to Twenty-First Century American Fiction, edited by Joshua Miller, Cambridge UP, 2021, pp. 63–78. Cambridge Core, https://doi.org/10.1017/9781108974288.005.