Creating Open XML documents from a template can help simplify your work and allow for changes to the look and feel of your documents without modifying your code. But in some cases, you'll want to create Open XML documents from scratch, without using an existing template.
There are two recent posts on my blog which you may find useful if you're looking to create documents from scratch:
CreateDocx sample programCreateXlsx sample program
The complete source code for these samples is included, and the posts include detailed information about how they work. They're in C#, but I've tried to document the details well enough to provide a blueprint for doing this from other platforms as well.
I'll also be putting together a PresentationML example soon, and we'll also begin posting a bunch of other code samples here shortly, but in the meantime I wanted to get these two on the site in case anyone wants to use them.
If there are other similar samples you'd like to see, post a comment here.