Here is an example of using the Text Field Picker in a plain html page:
<html>
<head>
<link href="https://developer.temenos.com/uux/base.css" rel="stylesheet" />
<script src="https://developer.temenos.com/uux/unified-ux-web.min.js"></script>
</head>
<body>
<uwc-text-field-picker label="Open The Picker">
<div slot="menu-content">
<uwc-text>My Content</uwc-text>
<uwc-checkbox label="Click here"></uwc-checkbox>
</div>
</uwc-text-field-picker>
</body>
</html>