Can we create three fake websites and three real websites and ask
them to spot what makes them fake?

It would definitely be possible to create 6 websites and be able to identify which ones are real and which are fake. Most of the ways to be able to tell would be in the details of the websites. For example, if certain names and dates don’t line up to the names of the company, that would be an easy tell. Things like small typos would also show which sites were real and fake because companies put a lot of care into their brand but if someone was only trying to scam you, they might omit minor details.