I just wanted to show you how much bleach, peroxide was left in the bottom of the box after sowing 6 sets of seeds.
Unfortunately the picture doesn't show actually how much was there, but the box was tilted on the side and had about 2 cups of bleach, peroxide on the bottom. If you have a lid that can hold that much liquid, I guess you could use the lid as the bottom. The lid to my glove box is flat inside with a lip going around it.
The lid on my glove box would NOT have held all of that liquid. So if you must make one with the lid for the bottom, make sure it can hold at least 1.5 - 2 cups of liquid safely.