I'm not sure though if Spence can score a knockout victory here, if he will ever win this fight, I think it will be a decision win for him and Fundora is very tough specially with how he showed in the Tim Tszyu fight.
Prior to him becoming a champion, if I'm not mistaken, he was in the top 5, and against Mendoza, he was leading in the judges scorecard, all 3 of them have Fundora by 4 or 5 points. Until Mendoza caught him with that huge punch that's why he was knockout. But if not for that, I think he could have won that fight.
But that one knockout loss by Fundora is a reference to all the fighters that want to beat him, I'm sure Spence watched and will continue to watch to spot Fundora's weakness and try to create a similar situation where he was knocked down.
The strategy that I can think of is Spence will try to get the match as close as possible so he can get his left hook he will go toe to toe here because as long as he is close to Fundora, Fundora has no advantage over him.
When you have that height advantage the body is an easy target if Spence worked on the body he would have a good opening in the face, Spence needs to win this fight and I'm sure he is so serious about his training because another defeat could be the end of his career.
I will say he just caught him at the right place at the right time,
https://www.youtube.com/watch?v=o6vfb-qFzRMIt was a left hook, Spence is not known to have power in his left hook and he himself was vulnerable to it, against Ugas and Porter Jr, but they just failed to capitalized it. Tim also try that strategy as well, but Fondura was a well aware of already and so he covers his left side once he throws his right hand.
Body could be a good target, I will agree to dhat, and that could be the plan of Spence before he go upstairs and trying to open up Fundora.