I cringe whenever I hear the word 'slice' in relation to web design. It sounds too much like the table days to me, even if it can be adapted to modern web design.
It's better to think of a web page primarily as HTML. That is, headings, paragraphs, lists, images and links etc. Plain, vanilla HTML. Then you bring in a bit of CSS. Create columns and other sections. Then add color, maybe some nice fonts, background images etc.
The slice approach, on the other hand, seems an artificial way to transfer print design—a static image—to the web, which is not really very practical. It makes it sound like you are not really adapting to the web.
What are you actually slicing? What components are you working with?