Just point me in the right direction, I'm happy to read and learn. But I just can fine a "sandbox" type draft workspace.
Here are some things you ought to be made aware of. You cannot build or use your own custom theme built from scratch at WordPress.com.
The only themes we can use are those found here > Appearance > Themes
This is a multiuser blogging platform. All blogs wearing the same theme are using the same underlying template and we cannot access the underlying files and edit templates or themes. http://en.support.wordpress.com/themes/editing-themes/
There are two free themes, Sandbox and Toolbox designed to allow maximum flexibility for CSS editing and creating new “skins”. Toolbox is more modern and includes a lot of support for CSS3 and HTML5, so it is really only limited by your skills and knowledge.
If you have CSS editing experience the upgrade will allow you to stylize the appearance of themes you find here > Appearance > Themes, but will not allow you to change the functionality, by editing the underlying template. It does not allow you to remove footer links to the theme designer or to WordPress.com. Also note that CSS is theme specific, so you cannot use the CSS stylesheets from other themes with the themes at WordPress.COM. http://en.support.wordpress.com/custom-design/custom-css/
See > Using WordPress.com to Create a Website http://en.support.wordpress.com/using-wordpress-to-create-a-website/
A WordPress blog can either be structured as a page based website or its conventional post based structure can be retained. That’s why understanding the differences between posts and pages, http://en.support.wordpress.com/post-vs-page/ comprehending the SEO implications of creating a page based structure, and knowing how to use custom menus http://en.support.wordpress.com/menus/
are key to decision making when selecting a theme, and setting up your WordPress.com blog. http://onecoolsitebloggingtips.com/2010/05/12/better-blogging-at-wordpress-com-pages-and-posts/
One one hand, none of the characteristic "blog" features likes categories, tags, authors, dates, etc. can be removed from a free hosted WordPress.com blog without purchasing an annually renewable custom design upgrade and doing the required CSS editing.
One that other hand, one can hack a WordPress.org theme free of charge. Have you read this comparison? WordPress.com and WordPress.org: The Differences http://en.support.wordpress.com/com-vs-org/