RX100 Filter Options?

I'd like to know who here uses some sort of filter on the lens of your RX100 and exactly how you attach it.
Also - how does that work since from the looks of it the lens completely closes down into the camera? Do you just attach it each time? Is it easy? Do you find it worth the trouble? Does it cause any kind of problems when using the flash? etc etc?

Be specific if you can, I am an amateur so I don't know all of the jargon quite yet - thanks so much for your replies.