Hux is busy, Kylo is a horny pest. Hux takes care of him by wanking him off while continuing to do his work with his free hand and not really paying him the attention that Kylo wishes, talking about work and barely looking at him and telling him off a bit/shushing him/telling him to hurry up and cum coz he needs both hands.

Bonus if he's wearing his glove and when Kylo cums he takes it off and throws it at him discarded before focusing on work with a clean hand coz work is more important than Kylo's need for intimacy.