Charming

My friend,s birthday is next week and I want to make her some mug rugs with Maxine fabric squares but what do I put between the fabric layers,warm and natural? Or insul??something or some thin layer of batting (I have really thin cotton batting)

Thanks for any help

Oh forgot to mention these are 7" squares. I sure hope they won't be big as I didn't want to lose any part of the design