Constructing a grid with many layers provides not only a framework in which to build your story and story world, but also provides the opportunity to test whether your story and characters work before committing a huge amount of time to writing. I’m sure we’ve all had the experience of getting three-quarters of the way through a story and realising it’s not working and we don’t know how it is going to end. However, this is a very process driven way to go about story writing and if you’re the sort who likes your characters to lead you all over the place, stop right here, because you will only feel frustrated.
To construct a multi-layered grid you start with the most basic elements of the story: The premise – often a ‘what if.....a boy were to meet a girl on a bus,’ etc.
Next you construct the characters, and the villain (arguably the most important character): who are they, what are they like, how do they relate to the villain of the piece, how do they relate to each other, what are they all after, how are they going to grow as individuals during the story?
Got your characters sorted? Now give each one a moral flaw and an immoral action in your story, this will make them much more interesting and give the other characters something to react against.
The thematic story line follows next: what is the story really about? What value are you trying to convey to your readers when they read this story. It could be a moral point, a political point or something quite ordinary like ‘true love never fails’ or ‘love needs more that true love,’ whatever takes your fancy. If your story has an underlying theme it will automatically have more depth.
Now you need to decide what everyone is after, this is the thing that drives all the characters to act and react against each other, it could be money, love, happiness, saving the world etc, though it doesn’t have to be what they eventually end up with.
Now map out your main scenes and briefly what happens in each, making sure each is a consequence of the actions taken by characters in the previous scenes.
At this point you should have a good idea if your story is going to work or lose its way.
You can carry on giving your framework more layers if you wish - it really depends on how much freedom or direction you want in your writing.