public class GraphicsLayerCreationParams : LayerCreationParams 

var map = MapView.Active.Map;
if (map.MapType != MapType.Map)
  return;// not 2D

var gl_param = new GraphicsLayerCreationParams { Name = "Graphics Layer" };
QueuedTask.Run(() =>
{
  //By default will be added to the top of the TOC
  var graphicsLayer = LayerFactory.Instance.CreateLayer<ArcGIS.Desktop.Mapping.GraphicsLayer>(gl_param, map);

  //Add to the bottom of the TOC
  gl_param.MapMemberIndex = -1; //bottom
  LayerFactory.Instance.CreateLayer<ArcGIS.Desktop.Mapping.GraphicsLayer>(gl_param, map);

  //Add a graphics layer to a group layer...
  var group_layer = map.GetLayersAsFlattenedList().OfType<GroupLayer>().First();
  LayerFactory.Instance.CreateLayer<ArcGIS.Desktop.Mapping.GraphicsLayer>(gl_param, group_layer);

  //TODO...use the graphics layer
  //

  // or use the specific CreateGroupLayer method
  LayerFactory.Instance.CreateGroupLayer(map, -1, "Graphics Layer");
});