Making gravel trays?

[J-Bomb]

I have read that you can take a metal pan or something like a trash can lid, sink it in a shallow part of the lake, and this will supposedly work well as a place for fish (bass and bream) to lay their eggs.
Has anyone tried this? How deep would be best. Seems like a good idea-maybe would keep the turtles and crawfish from eating some of the eggs.
-Just curious
-Thanks