Awesome that's a great idea! I have a plastic container with alfalfa pellets but they're clearly not enough for digging so he doesn't really care right now. How deep would you say is the dirt and sand in your container?
I measured the size of my enclosure and about how deep/wide would fit for it and still give a nice amount to dig. I also made sure I had something that could rest on top to act as a top and a ramp to get in and out of it.
I wouldn't pick the white again as it seems too light, and she'd prefer a darker space.