public LayerCreationParams( 
   CIMLayerDocument layerDoc
)

{
    //Get the LayerDocument from a lyrx file
    var layerDoc = new LayerDocument(@"E:\Data\SDK\Default2DPointSymbols.lyrx");
    //Get the CIMLayerDocument from the LayerDocument and use it to create LayerCreationParams
    var createParams = new LayerCreationParams(layerDoc.GetCIMLayerDocument());
    //Create a FeatureLayer using the LayerCreationParams
    //Note: Needs QueuedTask to run
    LayerFactory.Instance.CreateLayer<FeatureLayer>(createParams, MapView.Active.Map);
}

{
  // Note: call within QueuedTask.Run()
  {
    //Create with initial visibility set to false. Add to current scene
    var createparams = new LayerCreationParams(new Uri(sceneLayerUrl, UriKind.Absolute))
    {
      IsVisible = false
    };

    //cast to specific type of scene layer being created - in this case FeatureSceneLayer
    var sceneLayer = LayerFactory.Instance.CreateLayer<Layer>(
             createparams, MapView.Active.Map) as FeatureSceneLayer;
    //or...specify the cast directly
    var sceneLayer2 = LayerFactory.Instance.CreateLayer<FeatureSceneLayer>(
             createparams, MapView.Active.Map);
    //ditto for BuildingSceneLayer, PointCloudSceneLayer, IntegratedMeshSceneLayer
    //...
  }
}