It is a great design. I have a few comments, the shallow dish lower part would likely be better if it were a flat bottomed saucer shape similar to a deep under plant drip tray. They can fit is really small spaces I have female who is about 155cm long at about 4500 gm she fits in a 30cm by 10 cm round dish.

Make sure you do not have a fully closed circle as an entrance so if it get stuck (like after a big meal) it can still dislodge the hide and get in or out. Ceramic if left un glazed like a flower pot will hold moisture and if you were to soak it every week or so it would do wonders to keep humidity up.