You could try the needle and thread trick. I wouldn't 100% depend on it though. Your opinion of the sex of that chick may swing back and forth for a couple more weeks.
I'm brand new to raising chickens. This website has been loads of help! I started my journey with 2 blue copper marans and one splash marans chicks. They're about 8-9 wks old now, and I heard the very first attempt at a crow this morning!! Somewhat pathetic sounding, but awesome!! Thanks to...