themes-wordpress/assembler/templates/index.html

<!-- wp:template-part {"slug":"header"} /-->

<!-- wp:group {"tagName":"main","metadata":{"name":"Main"},"style":{"spacing":{"blockGap":"0","margin":{"top":"0"}}}} -->
<main class="wp-block-group" style="margin-top:0">
    <!-- CURRENTLY EMPTY -->
</main>
<!-- /wp:group -->

<!-- wp:template-part {"slug":"footer"} /-->