Coming from a construction/carpentry point of view here's my $.02:
- Deck screws are best, stainless steel also good.... avoid sheetrock screws though! You could also use bolts but this is overkill.
- To seal the screws, you could also plug the holes with silicone
- When getting yor 2x4's or 2x6's buy the straightest ones possible. There's also a higher grade of 2x4 you can buy that is straighter, has less knots, and has sharper corners. This is preferred for stand construction.
- Before you wrap your frame with plywood, seal it with a polyurathane or equavalent. This will protect it from the constant humidity..
- For glue, Liquid Nails works good. But, Gorilla Glue is better (Home Depot, Lowes carries it). This stuff is wicked strong. Make sure you glue your joints.
Kevin