Change Default Drop Zone For Custom Layout

main.js

AUI().ready(
     function(A) {
          var CustomLayout = A.one('LAYOUT_CLASS_NAME');
          if(CustomLayout){
               A.Do.before(function(option) {
                    if (!option.placeHolder) {
                         option.placeHolder = A.Node.create('<div class="loading-animation"></div>');
                    }
                    option.placeHolder.prependTo('TARGETED-COLUMN-ID');
               }, Liferay.Portlet, 'add', Liferay.Portlet);
          }
     }
);