<Grid Margin="12">
  <Grid.RowDefinitions>
    <RowDefinition Height="Auto"/>
    <RowDefinition Height="*"/>
  </Grid.RowDefinitions>
</Grid>

<StackPanel Orientation="Vertical" Margin="12" Spacing="8">
  <!-- дочерние элементы -->
</StackPanel>

<DockPanel LastChildFill="True">
  <Menu DockPanel.Dock="Top"/>
  <StatusBar DockPanel.Dock="Bottom"/>
  <Grid><!-- центр --></Grid>
</DockPanel>