Hum... clay aggregate, etc. can all be part of a false bottom set up. This link has discussion and drawings on building one with clay: Frog Forum - Building Dart Frog Terrariums / Tropical Terrarium Construction . Literally you will have a wet part and a dry one. The dry must start above the highest water level so soil does not become water logged, breeds bacteria, and drowns most plants. That is where either an egg crate or similar frame or a huge amount (if large vivarium) of clay balls or similar come into play.
Clay balls (or sintered glass, ceramic, lava, etc.) are porous and will harbor a colony of de-nitrifying bacteria. But are heavy when wet and in large set-ups, the weight can be significant. Egg crate or similar framing is lightweight; but does not provide the surface area for colonizing bacteria the way porous materials do. For smaller set-ups just building up a platform of balls to keep soil above water table is fine. For larger set-ups; the use of an egg crate frame can help keep weight down and clay balls are costlier too. Have also seen a thin (couple ball thickness layer) of clay balls between the egg crate and soil; with netting on both sides in use. Hope this helps and good luck!