I usually set the layout like this where I specify the gap inside the VerticalLayout tag

<s:Group>
   <s:layout>
      <s:VerticalLayout gap="10"/>
   </s:layout>
</s:Group>

I'm trying to specify the layout as a property of the Group like this

<s:Group layout="{new VerticalLayout()}">
</s:Group>

but not sure how to specify the gap in this case. Couldn't spot something in the documentation to show if it's possible to include gap as a parameter when creating new VerticalLayout or what its position would be.