console
ClassicEditor
.create(document.querySelector('#editor'))
.catch(error => {
console.error(error);
});
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>CKEditor 5 - Classic editor</title>
<script src="https://cdn.ckeditor.com/ckeditor5/27.1.0/classic/ckeditor.js">
</script>
</head>
<body>
<h1>Classic editor</h1>
<form action="[URL]" method="post">
<textarea name="content" id="editor">
<p>This is some sample content.</p>
</textarea>
<p><input type="submit" value="Submit"></p>
</form>
</body>
</html>