I use with huge success those shallow and wide plastic dishes that's meant to be put under multiple small plant pots. Not sure how you name it in English. At first I tried with Tupperware style dishes, but the problem occurred quickly. When they threw out most of the sand, the dish became light and when someone stepped on the edge, they ended up underneath and the dish was upside down on their head like a dome. Luckily I had more free time back then to check them regularly. A few months later I came across to a post in this forum that one of their quail did the same in the heat of the summer and died because of it. After that I never used my tupperware again.