What to use since Marionette Application Regions are deprecated - backbone.js

Question

I am confused by the Marionette (2.3.0) documentation from the link below that says the Application Regions feature is deprecated. A Layout View should be used instead. Does that mean I should not use MyApp.addRegions() any more? Then how should I add my Layout View to my application?
http://marionettejs.com/docs/marionette.application.html#application-regions
Application Regions
Warning: deprecated This feature is deprecated. Instead of using the
Application as the root of your view tree, you should use a Layout
View. To scope your Layout View to the entire document, you could set
its el to 'body'. This might look something like the following:
var RootView = Marionette.LayoutView.extend({ el: 'body' });

Answer 1

I will like to explain with a very simple example the usage of layout view in marionette.
html
<div id="appDiv"></div>
<script type="text/template" id="mainTemplate">
<div id="div1"></div>
<div id="div2"></div>
</script>
<script type="text/template" id="itemTempFirst">
<p>some text item 1 view</p>
<p>some text item view 1</p>
</script>
<script type="text/template" id="itemTempSecond">
<p>some text item 2 view</p>
<p>some text item view 2</p>
</script>
JS Code:--
var app = new Marionette.Application();
var LayoutViewObj = Marionette.LayoutView.extend({
template:"#mainTemplate",
el:"#appDiv",
regions:{
reg1:"#div1",
reg2:"#div2"
}
});
var layoutViewInstance = new LayoutViewObj();
layoutViewInstance.render();
var ItemView1Obj = Marionette.ItemView.extend({
template:"#itemTempFirst"
});
var ItemView2Obj = Marionette.ItemView.extend({
template:"#itemTempSecond"
});
var item1 = new ItemView1Obj();
var item2 = new ItemView2Obj();
layoutViewInstance.getRegion("reg1").show(item1);
layoutViewInstance.getRegion("reg2").show(item2);
Please note I was trying without el element earlier , but i got no luck and as I used el:"#someElem" life got easier