<ad:LayoutAnchorablePane DockHeight="Auto" x:Name="LeftTools">
</ad:LayoutAnchorablePane>

dockSite = new LayoutAnchorable();
LeftTools.Children.Add((LayoutAnchorable)dockSite);

// In Constructor
ObservableCollection<LayoutAnchorable> LeftToolList = new ObservableCollection<LayoutAnchorable>();

// Property
public ObservableCollection<LayoutAnchorable> LeftToolList { get; set; }

<ItemsControl ItemsSource="{Binding LeftToolList}">
   <ItemsControl.ItemsPanel>
      <ItemsPanelTemplate>
         <ad:LayoutAnchorablePane/>
      </ItemsPanelTemplate>
   </ItemsControl.ItemsPanel>
</ItemsControl>