maui-linux/Xamarin.Forms.Controls/GalleryPages/ControlTemplateXamlPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="Xamarin.Forms.Controls.GalleryPages.ControlTemplateXamlPage">
  <ContentPage.Resources>
    <ResourceDictionary>
      <ControlTemplate x:Key="ViewTemplate">
        <StackLayout>
          <Label Text="{TemplateBinding Parent.AboveText}" />
          <ContentPresenter />
          <Label Text="Below" />
        </StackLayout>
      </ControlTemplate>
      <Style TargetType="ContentView">
        <Style.Setters>
          <Setter Property="ControlTemplate" Value="{StaticResource ViewTemplate}" />
        </Style.Setters>
      </Style>
    </ResourceDictionary>
  </ContentPage.Resources>
  <ContentView>
    <Label Text="I R CONTENT" />
  </ContentView>
</ContentPage>