If your oven runs hot or you cook at a slightly higher temperature, check the rice towards the end of the cooking time and add a splash of water if needed to stop it drying out. The rice should be soft and slightly saucy. If it looks a little dry at the end, just stir through a splash of water or stock to loosen it back up.

Troubleshooting:
Make sure to use easy cook-long grain rice.

Make sure the chicken is spread in a single layer on top, leaving the rice underneath so it cooks properly.
Rice still firm
Add a splash of water or stock, cover and return to the oven for 5-10 minutes.
Rice too dry:
Stir through a splash of water or stock before serving.
If the bake is too wet:
Return to the oven uncovered for a few extra minutes to reduce.