Yeah, it's hard, there were plenty of presentations I had to do on topics I didn't care too much about either. In those cases, it just helps to really know your stuff and if you can't grasp everything, just try to grasp as much as you can, cover what you do know, and then fill in the gaps with other relevant material outside the scope of what the original assignment addressed, but still relates and can tie into what you presented earlier (kind of like a DLC). It also helps if you like and/or you know some good details of that additional "DLC" you're adding in there.

I had to do a 45 minute presentation on The Innovator's Dilemma and I covered most of the basics that the book went over, but with that much time to kill, I accompanied the presentation on the generation of where new ideas come from (as a potential origin source for what may cause disruptive innovation). Worked like a charm even though those last fifteen minutes weren't quite what was specifically addressed in the book, but I took it as an approach to find ways to go beyond that scope (and it allowed me to incorporate a fun video on YouTube that addressed this). And covering that kind of stuff was interesting and fun. Aced it, and that presentation was a big part of the final grade.