My personal experience is also that Flag beach is for intermediate->advance riders, not just because of all the rocks but also because of the "helpful" flagbeach people.
When I was there a guy dropped his kite in the water(looking out to sea, on the left hand side going around the corner into the harbour).
Anyway, I was sitting on the beach with these guys, they saw the guy struggling and not getting his kite up. There's a lot of real nasty rocks on that side, if you get taken there, that's it, you and your kite are going to get some serious damage. Eventually the lifeguards(from a different beach) came driving up on their quadbike to inform these guys that there's a guy in trouble. FB response was.....we aren't life guards and that guy didn't pay for rescue.
Fair enough, they didn't wanted to just rush out and pick up the guy and charge him a fortune for rescue, but he was drifting/struggling a long time, heading straight for the rocks, and they knew there is this point of no return where you won't even be able to get to the guy in the boat and then he is straight onto the rocks. He eventually had his kite damaged on the rocks as he swam out. I was a bit ****** with the FB guys....and made damn sure I didn't get in trouble for the rest of the time, even though I did pay for rescue services.
If you don't already know what you are doing....then don't go there.