What would you say is the best way to go about selling my MCOR Iris printer that is in good working condition?

3Dprinterclassifieds, gumtree, craigslist, ebay, 3D printer facebook groups, 3Dprint reddit subreddit are the places that jump to mind.

Just be aware that you are unlikely to get anywhere near the retail price. I bought one around 6 months ago and it’s almost criminal how little I paid for it.