To add static block over the Place order button!, you need to declare a PHTML file in checkout index anywhere in theme.
STEP 1:
Create a new XML file in theme
checkout_index_index.xml
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
<body>
<referenceContainer name="content">
<block class="Magento\Framework\View\Element\Template" name="static_block" template="Magento_Theme::block/summary.phtml" cacheable="false" />
</referenceContainer>
</body>
STEP 2 : create a PHTML file in below location
app/design/frontend/{theme_package}/{theme_name}/Magento_Theme/templates/block/summary.phtml
<?php
$summaryBlockDetail = $block->getLayout()->createBlock('Magento\Cms\Block\Block')->setBlockId('new-block')->toHtml() ?>
<script type="text/javascript">
window.summaryBlockDetail = "<?= json_encode($summaryBlockDetail)?>";
</script>
STEP 3 :
Add below code in .html file else any where in .html in checkout
view/frontend/web/template/place-order.html
<div class="component-wrapper">
<div class="control">
<span data-bind="html: summaryBlockDetail"></span>
</div>