You need to create two files for custom layout
1 - Create layouts.xml
app/design/frontend/Vendor/yourtheme/Magento_Theme/layouts.xml
This file will registered custom layout
<?xml version="1.0" encoding="UTF-8"?>
<page_layouts xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/PageLayout/etc/layouts.xsd">
<layout id="custom">
<label translate="true">custom layout</label>
</layout>
</page_layouts>
After creating above file you can check your custom layout in admin panel.
2 - Create custom.xml
app/design/frontend/Vendor/yourtheme/Magento_Theme/page_layout/custom.xml
This file will manage design for your layout page.
<?xml version="1.0"?>
<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_layout.xsd">
<update handle="empty"/>
<referenceContainer name="page.wrapper">
<container name="header.container" as="header_container" label="Page Header Container" htmlTag="header" htmlClass="page-header" before="main.content"/>
<container name="page.top" as="page_top" label="After Page Header" after="header.container"/>
<container name="footer-container" as="footer" before="before.body.end" label="Page Footer Container" htmlTag="footer" htmlClass="page-footer"/>
</referenceContainer>
</layout>
Now, flush the cache and check the new custom layout in admin panel configuration setting.
