I have used washed out milk jugs/water jugs. I cut a hole big enough for the quail to get in. I put a 1/2 inch of sand in the bottom. (the milk jugs ..plastic kind) have flat sides, so they stay stable while a quail sits in there, dustbathes, or lays an egg.
I have also used Peter Marshalls Grass Cave (made for rabbits) you can find them on
Amazon or on the big box pet stores online, like
petco etc.
I also wash and cut a hole in the top of my used empty cat litter jugs. Once again, they lay flat, are covered on all sides but the hole you have cut on the top large enough for quail.
My little trio, and now a new batch of 5 4wk olds use the milk jug and cat litter jug sand boxes alot. I also offer the used containers from organic baby spinach. You know how they sell them prepackaged in the clear plastic box with lid? At my house it serves two purposes. We all eat the baby spinach (human and quail) then I rinse and put 1/2 inch to an inch of sand mixed with pine shavings in it, and viola! Small sandbox for teen and preteen quail.
Get creative and look around for things that you would normally throw away and cut a nice big hole for them to climb into.
Many animals do not like to go into things that are one way in, one way out. It is threatening to the animal. I have solved many a cat not using the litter box client, this way. I move the cat box out, so that the cat can see any "attackers" in the house, whether it be the dog, or the other cats. They then feel safe enough to use the restroom real quick and leave.
I digress... but you get the point.
Tonya