This is a good way to utilize the “wasted” space on your projects.
Double check the dimensions on the inserts, as they vary between suppliers.
These are the specific ones I used on these:
We use cookies to personalize content, interact with our analytics companies, advertising networks and cooperatives, and demographic companies, provide social media features, and to analyze our traffic. Our social media, advertising and analytics partners may combine it with other information that you’ve provided to them or that they’ve collected from your use of their services. Learn more.