[noodlesUK]

It's usually pretty easy to tell tbh. Unlike buying online you can inspect the goods as they are right there in front of you. There's usually a pretty noticeable difference between Alibaba "artisanal" stuff and the real McCoy. In any case, I suspect that at a lot of markets, if someone were to be coming in and selling stuff under totally false pretences, the other stalls would get their pitchforks out.

You can also chat to the person and see if they're knowledgable about their stuff. Depending on the craft, the person might actually be doing it in front of you (or customise their goods somehow).