When you're brainstorming on your laptop and plain text just won't cut it to express your ideas, you might need an extra workspace you can actually draw on. Why not add a quick, erasable surface to your laptop for an added level of expression?
Charles Han used common whiteboard adhesive paper that you can buy at an office supply store to create a writable surface on his laptop lid. And rather than just stick it to the actual surface of the laptop, he used a cheap MacBook case to make it easier to remove. The rest is pretty self-explanatory; you just need to trim the whiteboard adhesive to the correct size, and round the corners if you want a good fit for your device. The hard part is applying the sticker without getting unseemly air bubbles. Han used plastic card (like a credit card) to iron out any imperfections.
It's a little silly but I think it's a great idea. Sometimes I need to way to help visualise my ideas, and using the laptop lid adds a layer of convenience that could even help with your collaborations and presentations.