The Internet is full with research reports on any subject you ever wanted to explore. In theory therefore, it should be easy to Google together a pile of slides on a certain subject, "Frankenstein" a deck together and go on stage as an expert in a particular field.
Unfortunately, it is not that simple. The audience will figure out very quickly when your knowledge of a subject is exactly the amount of content that is written on the slides. It shows in the way you answer questions, it shows in the way you present your slides.
This can often happen when an executive in the technology industry gets invited for a conference to speak about "the latest in [fill in technology buzzword]". People take too little time to prepare their talk, and the result is a stumbling performance that recycles some cliches about the subject.
The same is true in consulting firms, where a junior analyst gets charged with "pulling some slides together" on a subject and gets sent of to present to client at the last minute to stand in for a more senior consultant who could not make the slot.
What to do?
Option one is to adjust the topic you are speaking about, often conference owners will be open to this. Speak about something that is really close to what you do day to day. Even if you do not answer the big question on this huge issue everyone is thinking about, that very personal, very specific experience that you have will be very valuable.
The other option is to do the homework properly. Go beyond the fluffy research reports, dive in, become an expert. See which reports are smart, which ones contradict each other, which ones are just buzzwords. My experience as a management consultant shows that in 1-2 weeks of hard work you can reach a knowledge level that becomes interesting for an uninformed audience to listen to.
(Side note: a 2 second slide created in my presentation app SlideMagic to illustrate the concept. The exact spirit of the app: sketch something simple quickly, that explains the concept, and move on. You can do better things with your time than sweating over complicated presentation design software)