Warp core assembly was a type of maintenance performed on a Starfleet vessel's warp core by an engineering team.
In 2371, Lieutenant B'Elanna Torres met Kes in engineering of the USS Voyager. Unknown to Torres was the Kes she was talking to had time traveled from 2376. To make up an explanation for her appearance in engineering to Torres, Kes told her that Captain Kathryn Janeway had requested that she become more familiar with Voyager. In response, Torres asked Kes if she wanted to observe her and her team perform a warp core assembly. However, Kes declined her invitation. (VOY: "Fury")