Using one wifi radio as client?

I have a Flint 2 and I'm trying to use the 2.4g radio as a client to another wifi network and the 5g radio as an access point/router. I can't find a way to do so within the normal interface, and using LuCI, the wireless client never connects, and upon reboot, the configuration is deleted entirely.

Repeater mode is what you are looking for: Repeater - GL.iNet Router Docs 4