|| It depends on your need, time and access to the site source code. ||
Consider a scenario when you need it for a short time, don't want to go in a lengthy site publishing cycle to add and then remove it from the site or you have limited access to the source code. If any of the above reason suites your requirements than Adobe Tag manager is your best friend.
How to do it right -
1. Identify the page where you want to position it.
2. Add a placeholder container e.g. <div id="placeholder" /> on your page or find an existing container and reference to its id or class property to inject your widget.
3. Create a page based rule in DTM with condition match with your identified page. It should fire when DOM is ready.
4. Use Third-party Script section and Non-sequential HTML section to add your snippet followed by widget script.
5. Save and publish.
Issue: You may observe flicker while loading widget on site. You actually don't have control over its load timing.