Stick Layout in Xamarin Forms to bottom

<StackLayout>
  <StackLayout Orientation="Horizontal" VerticalOptions="Start">
    <!-- top controls -->
  </StackLayout>

  <StackLayout VerticalOptions="CenterAndExpand">
    <!-- middle controls -->
  </StackLayout>

  <StackLayout Orientation="Horizontal" VerticalOptions="End">
    <!-- bottom controls -->
  </StackLayout>
</StackLayout>

Make sure to have no more than one child with Expand options for best performance.

You can use VerticalOptions to send layout to bottom.

var stacklayout = new stackLayout()
{
     VerticalOptions = LayoutOptions.EndAndExpand
     Children = {
      //your elements
     }
}

Within a RelativeLayout I got the best results with defining the Height- and Y-Constraint.

<RelativeLayout>
        <StackLayout VerticalOptions="Start" BackgroundColor="Green"
                    RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1}"
                    RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.25}">
          <!-- Top Content -->
          <Button Text="Top Button" Clicked="Button_OnClicked" />
        </StackLayout>

        <StackLayout VerticalOptions="Center" BackgroundColor="Aqua"
                          RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1}"
                          RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.30}"
                          RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.6}">
          <!-- Mid Content -->
          <Button Text="Mid Button" Clicked="Button_OnClicked" /> 
        </StackLayout>

        <StackLayout VerticalOptions="End" BackgroundColor="Yellow"
                          RelativeLayout.WidthConstraint="{ConstraintExpression Type=RelativeToParent, Property=Width, Factor=1}"
                          RelativeLayout.YConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.90}"
                          RelativeLayout.HeightConstraint="{ConstraintExpression Type=RelativeToParent, Property=Height, Factor=0.1}">

          <!-- Bottom Content -->
          <Button Text="Bottom Button" Clicked="Button_OnClicked" />
        </StackLayout>
</RelativeLayout>

Results:

Have you figured it out yet? If not, there is a few ways you could accomplish this: Note that i've got the same problem my self, but this is my theory:

So that you could have a StackLayout in which you populate it with three "main childeren". The first could be a absolute or relative layout (I don't know the difference that well yet). In theory you should be able to add a element to the absolute layout and then add elements on top of the first element, because absolute layout uses a z-index, which works like layers in photoshop. So in other words do it like this:

var topAbsoluteLayout = new AbsoluteLayout();

            topAbsoluteLayout.Children.Add(header, new Point(0, 0));
            topAbsoluteLayout.Children.Add(element1, new Point(x,y));
            topAbsoluteLayout.Children.Add(element2, new Point(x, y));

Then you should do the same thing with the footer and remember to add topAbsoluteLayout to the Childeren in the StackLayout.

I hope this helps you out