Submerge the wood in water for at least 3 days. A steam "box" can be a plastic bag over a boiling kettle! Anything will work as long as it holds the steam. Always wear gloves and be careful around steam! You can dry wood out by steaming it for too long. For thin stuff of 1/4" thickness 5 or 6 mins is enough - depending on the wood. Do a few test runs to work out the bugs.

Redwood is poor for steaming so you might be better off with cutting thin strips and laminating them.