Prepare a list of statements ahead of time, about half of which are completely wrong. It shouldn’t be difficult for people with basic knowledge of the topic to spot which ones they are.
In the session, show the list and have people mark the correct ones in one way and the incorrect ones in another way.
When everyone has made their marks, encourage them that they already know lots about the topic. If there are any statements with a mix of different marks, note the difficulty. Resolve it right away by explaining what you think the right answer is. Consider re-wording or changing that entry for the next time you use this exercise.
By design, this exercise shouldn’t be difficult and items shouldn’t be ambiguous. If people struggle then you’ve either misjudged how much they know already, or expressed yourself poorly.
Put the statements on sticky notes on a virtual whiteboard and give people emojis to copy next to them. Alternatively have a bullet list in a shared document and have people paste an emoji next to them. Provide pretty emojis that preferably on topic. A bomb for wrong items, a tick for correct ones, that kind of thing.
It’s pretty quick to do and gets everyone feeling good about already knowing something about the topic. The emojis make it look attractive.