In order to make starting a new theme relatively simple I took the blackcandy theme and just turned it in to a generic CSS/HTML framework (i.e. no images just blocks and buttons) which I use at the start of every project. This makes creating a page layout very quick and keeps the same CSS id's and Classes, which means moving code between projects is much easier and also helps to keep things cross browser compatible (as the initial template is x browser). I'd be happy to upload this framework if anyone wants it.
Here is a brief outline of how you convert a static HTML page into a .ss template.
Because .ss files are basically HTML files with <% %> and $ tags placed where we want SS to fill things with the content from the database, it's a relatively simple process.
To start with just make your main Page.ss file, a complete page including some (possibly dummy) content which can be sliced up into separate elements later. So in the <head> we can replace the Links and meta tags with <% base %> and $MetaTags and then instead of an HTML menu which might look like this:
We can replace it with the same SS menu which will look something like this (you can find more on this in tutorial 1):
<% control Menu(1) %>
<% end_control %>
This carries on, adding $Content in place of your content text, $Image to instead of an <img> tag etc. etc. until you have a page which looks the same through SS as it does in plain HTML.
Once you have that you can then chop out your <div id="content class="typography"></div> block and put it into /Layout/Page.ss replacing it with $Layout in the main Page.ss file (again more on this in tutorial 1).
Then you can decide what you want to chop out and add as an <% include %>, so you might take out your second level menu block and place that in Includes/Menu2.ss replacing it with <% include Menu2 %> in the templates you want to have a Menu 2.
At this point you should pretty much have a SS theme which you cant then extend as far as you like.
If you are confident with CSS and HTML you should have no trouble building SS templates. It really is one of the most designer friendly templating system I have come across (granted I haven't tried that many, I got hooked on SS ;) ).
And of course if you get stuck you can always come and ask us :)