I can’t take credit for the idea, I saw it posted either here or on the framework subreddit (?). I bought two of these to protect my framework 13" (200x300x2): 200X300 100% 3K Carbon Fiber Sheet Laminate Plate Panel 0.5-4MM Thickness | eBay
Then for the 16" I bought two custom 270x360x2 sheets. Those should be arriving today or tomorrow.