Here is how I make a left turn in that situation. About 600ft before the intersection I look for a gap in the traffic so I can occupy the left hand part of the lane. As I make that maneuver I stick my left hand straight out briefly to tell drivers behind me I’m turning. It’s the drivers following me who’s cooperation I need, drivers facing me not as much. As I arrive at the intersection both my hands are in the drops because I may have to stop or maneuver suddenly. Drivers in the intersection may not have seen my hand signal, but should understand my intention to turn left from my road position.