Oilcloth by the Yard and there are so many fun patterns. After the sides are stitched, I just added a couple circles of Velcro on the flap.
There! Ok, now microwave the cotton pouch ONLY for about a minute, then place inside the oilcloth and put in your nest box. Do not microwave the oilcloth. I'll add a thick layer of shavings on top of this to hopefully keep the eggs from cooking and the pouch to get soiled. I'll add it in the morning and see how the chickies like it!