The slide carb should be closed "all the way" - ie, if you were to put the brakes on your carb shouldn't close any more.

You use the idle screw to adjust how much air gets through when the engine is in this state, and the usual seems to be a 1mm gap when you peer down the carb (take the air filter off first!)

If you're gonna adjust the idle, open the throttle first to avoid damaging the needles.