First of all Get the nose down -- your first priority is to maintain flying speed.
Once at best glide, use the available time to consider your options and if time permits, try to get the engine going again: fuel on, primer locked, carb heat on.
From 50' you'll likely be on the ground before you have time to get your hand to the flap control.
Pick the softest spot and land there.
It helps to know the terrain about your local field and pick places ahead of time where you can try to put the plane down in various situations. A good time to review these locations is at the end of the takeoff checklist.