Actually, I used plexiglass. I had my little Physics major son help me plan the best approach for the water vs. soil pressure.
Honestly, I think the snowball started because i was too overzealous. I wanted her in her tank so bad that I did not wait the requisite 48 hours for the aquarium sealant to cure before adding the pressure of the water and dirt.
Anyway, here's two pictures - not the greatest. One is a top view of how the plexiglass was set up; the other is how it looked for the first few hours

It's OK, though...I'll live with a yucky bin for now - - I have grand plans for her ongoing non-nesting environment
and, when I set that up, trust me I'll wait 48 hours for the sealant.
Another line entry in my lessons learned book.