RelativePanel is a layout container that is useful for creating UI that do not have a clear linear pattern
If your UI consists of multiple nested panels, RelativePanel is a good option to consider.

You can use the additional properties of RelativePanel to relatively layout its content. See: RelativePanel Class

public class RelativePanel : Panel

Attributes

Property	Description	Default Value	Remarks
Above	Make this element above the target element
AlignBottomWith	Align this element with the bottom of the target element
AlignBottomWithPanel	Align this element with the bottom of the Panel	false
AlignHorizontalCenterWith	Align this element horizontally with the target element in the center
AlignHorizontalCenterWithPanel	Align this element horizontally with the Panel in the center	false
AlignLeftWith	Align this element with the left side of the target element
AlignLeftWithPanel	Align this element with the left side of the Panel	false
AlignRightWith	Align this element with the right side of the target element
AlignRightWithPanel	Align this element with the right side of the Panel	false
AlignTopWith	Align this element with the top of the target element
AlignTopWithPanel	Align this element with the top side of the Panel	false
AlignVerticalCenterWith	Align this element with the target element vertically in the center
AlignVerticalCenterWithPanel	Make this element and Panel vertically aligned in the center	false
Below	Make this element below the target element
LeftOf	Make this element to the left of the target element
RightOf	Make this element to the right of the target element

Case

<hc:RelativePanel Width="620" Height="700" Margin="32">
    <Border Name="Rect1" Background="{DynamicResource DangerBrush}" Height="50" Width="50">
        <TextBlock Text="Rect1" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect2" Background="{DynamicResource PrimaryBrush}" Height="50" Width="50" hc:RelativePanel.AlignHorizontalCenterWithPanel="True">
        <TextBlock Text="Rect2" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect3" Background="{DynamicResource SuccessBrush}" Height="50" Width="50" hc:RelativePanel.AlignRightWithPanel="True">
        <TextBlock Text="Rect3" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect4" Background="{DynamicResource DangerBrush}" Height="50" Width="50" hc:RelativePanel.AlignBottomWithPanel="True">
        <TextBlock Text="Rect4" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect5" Background="{DynamicResource PrimaryBrush}" Height="50" Width="50" hc:RelativePanel.AlignBottomWithPanel="True" hc:RelativePanel.AlignHorizontalCenterWithPanel="True">
        <TextBlock Text="Rect5" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect6" Background="{DynamicResource SuccessBrush}" Height="50" Width="50" hc:RelativePanel.AlignBottomWithPanel="True" hc:RelativePanel.AlignRightWithPanel="True">
        <TextBlock Text="Rect6" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect7" Background="{DynamicResource PrimaryBrush}" Height="50" hc:RelativePanel.RightOf="{Binding ElementName=Rect1}">
        <TextBlock Text="Rect7 (RightOf Rect1)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect8" Background="{DynamicResource SuccessBrush}" Height="50" hc:RelativePanel.Below="{Binding ElementName=Rect7}">
        <TextBlock Text="Rect8 (Below Rect7)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect9" Background="{DynamicResource PrimaryBrush}" Height="140" Width="460" hc:RelativePanel.AlignHorizontalCenterWithPanel="True" hc:RelativePanel.AlignVerticalCenterWithPanel="True">
        <TextBlock Text="Rect9" Padding="10" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Top"/>
    </Border>
    <Border Name="Rect10" Background="{DynamicResource DangerBrush}" Width="50" hc:RelativePanel.RightOf="{Binding ElementName=Rect9}" hc:RelativePanel.AlignVerticalCenterWith="{Binding ElementName=Rect9}">
        <TextBlock Text="Rect14 (RightOf Rect9, AlignVerticalCenterWith Rect9)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center">
            <TextBlock.LayoutTransform>
                <TransformGroup>
                    <RotateTransform Angle="-90"/>
                </TransformGroup>
            </TextBlock.LayoutTransform>
        </TextBlock>
    </Border>
    <Border Name="Rect11" Background="{DynamicResource DangerBrush}" Height="50" hc:RelativePanel.AlignBottomWith="{Binding ElementName=Rect9}" hc:RelativePanel.AlignHorizontalCenterWith="{Binding ElementName=Rect9}">
        <TextBlock Text="Rect11 (AlignBottomWith Rect9, AlignHorizontalCenterWith Rect9)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect12" Background="{DynamicResource DangerBrush}" Height="50" hc:RelativePanel.Below="{Binding ElementName=Rect8}" hc:RelativePanel.AlignLeftWith="{Binding ElementName=Rect7}">
        <TextBlock Text="Rect12 (Below Rect8, AlignLeftWith Rect7)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect13" Background="{DynamicResource PrimaryBrush}" Height="50" hc:RelativePanel.Below="{Binding ElementName=Rect12}" hc:RelativePanel.AlignRightWith="{Binding ElementName=Rect12}">
        <TextBlock Text="Rect13 (Below Rect12, AlignRightWith Rect12)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect14" Background="{DynamicResource SuccessBrush}" Height="50" hc:RelativePanel.Above="{Binding ElementName=Rect9}" hc:RelativePanel.AlignRightWith="{Binding ElementName=Rect9}">
        <TextBlock Text="Rect14 (Above Rect9, AlignRightWith Rect9)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
    <Border Name="Rect15" Background="{DynamicResource DangerBrush}" Height="50" hc:RelativePanel.LeftOf="{Binding ElementName=Rect2}" hc:RelativePanel.AlignTopWith="{Binding ElementName=Rect9}">
        <TextBlock Text="Rect15 (LeftOf Rect2, AlignTopWith Rect9)" Padding="10,0" Foreground="White" FontWeight="Bold" HorizontalAlignment="Center" VerticalAlignment="Center"/>
    </Border>
</hc:RelativePanel>