Welcome aboard.

What I would do is, place a drainage layer in the tank, either by using a false bottom or simply a layer of Hydroton (LECA) or pea gravel. A drain pipe will be need to run down to the drainage layer. It should be capped when not being used to remove excess water. It should also be wide enough to allow a siphon hose to be incerted into it. I would also notch the bottom end to allow better water flow.
To build a false bottom see the red-eye article.
To go simple, place about a two inch layer of Hydroton on the bottom of the tank. Remember to place the drainage pipe first.If you are unable to get Hydroton, you can either use pea gravel or ZooMed's Hydroballs. Pea gravel is heavy and Hydroballs, even though a form of LECA, are just not as good as Hydroton, they are more expensive and are inconsistant is size.
Place a nylon screen mesh on top of the drainage layer, with a hole cut into it for the drain pipe. On top of of that, place a layer of ground coconut deep enough to plant in. Than plant plants into it. In the final step, cover substrate with leaf litter. The best leaf to use for this is "live oak", available from Josh's Frogs or from FF member JimO. "Live oak" is best because it doesn't break down as quickly as other types of leaves.
To make the set up more interesting, you can slope the substrate higher on one side or just add branches to climb on.