Built-in “writing board” to avoid pen imprints

It’d be great if Rocketbooks had a built-in shitajiki style writing board you could slip under the sheet you’re writing on so that your writing wouldn’t leave an imprint on the pages. It could just be a flap that folds out of the covers (made of the same material) so there aren’t any loose pieces to fall out and get lost or bent. Putting it on both covers would make sure you could use it with both the fronts and the backs of the pages, keeping them smooth and usable as long as possible.