<Instance ref.Class="sample::StackControl">
  <CustomControl>
    <Stack AlignmentToParent="left:0 top:0 right:0 bottom:0" Padding="5" Direction="Horizontal">
      <StackItem PreferredMinSize="x:100">
        <SolidBorder Color="#FFFF00"/>
      </StackItem>
      <StackItem PreferredMinSize="x:100">
        <SolidBorder Color="#FF00FF"/>
      </StackItem>
      <StackItem PreferredMinSize="x:100">
        <SolidBorder Color="#00FFFF"/>
      </StackItem>
    </Stack>
  </CustomControl>
</Instance>