I was using the standard flattie setup. Snapper sinker on the bottom - 12 ounce to stay on the bottom close to the boat, but could still feel the bites - 20 pound braid and 2 droppers above. Size 4 long shank hook, and baits were small slimey strips about 1.5 cm long, threaded on a few times. Have also caught them on spikey flattie strips of the same size. It appears they eat most things, maybe even a small squid strip, though have not tried it.
Smaller hooks would be better, however, some flatties can be caught amongst the whiting, and the smaller hooks would not be strong enough for a reasonable sized flattie in deep water.