Unfortunately ant powder only works with non-flying ants who take it down into the nest as food. Fly spray will work on flying ants, as would a flytrap. The ant powder will take a long time to completely wipe out the whole nest.
Ant powder is the best way, it kills flying ants as well (sorry Lardybloke) but they can be difficult to get rid of. the best way is get the gas fire out then clean out any debri,cover the entire area with ant powder and mix some sugar with ant powder, this way they will ingest the powder directly, you may have to do this a few times to get rid of them, im a pest controler and I find this method very sucsefull.