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class Selectpage implements MagentoFrameworkOptionArrayInterface{
    public function toOptionArray()
    {
        $options = [
            [
                'label' => __('-- Please select --'),
                'value' => '',
            ],
            [
                'label' => __('Home Page '),
                'value' => '1',
            ],
            [
                'label' => __('404 Page'),
                'value' => '2',
            ],
            [
                'label' => __('About Page'),
                'value' => '3',
            ],

        ];
        return $options;
    }

<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" layout="1column" xsi:noNamespaceSchemaLocation="../../../../../../../lib/internal/Magento/Framework/View/Layout/etc/page_configuration.xsd">
    <head>
        <title>Sample Paage</title>
        <css src="Namespace_Module::css/mycsss.css"/>

    </head>
     <body>
        <referenceContainer name="content">
            <block class="NamespaceModuleBlockPopupIndex" name="popup_index" template="popup/index.phtml">
            </block>
        </referenceContainer>
    </body>
</page>