If you only care about SEO, most of this wouldn’t matter for general web search engines (like Google, Bing, DuckDuckGo, etc.). It’s relevant if you care about semantic markup (which can be useful for various consumers and tools).
There is no general answer for this (just like your "basic HTML5 layout" cannot be used like that for many pages).
It depends on what the slider is about, what the previous content is, and what the following content is.
For example, if the image slider gives an introduction about your company on the homepage, the correct place would be the
header of the
body sectioning root:
<header><!-- image slider here --></header>
If the slider is the main content of the page (e.g., a page titled "Impressions" and the slider contains all the images), it should be in
<article><!-- image slider here --></article>
If the slider is just giving some eye candy, or suggestions for other pages the user might be interested in,
aside would be appropriate:
<aside><!-- image slider here --></aside>
And so on.
A good way for deciding if a sectioning element (
aside) should be used, is answering the question: Should it be part of the document’s outline?
If yes, a sectioning element should be used, and unless the content matches the definitions for
aside, the "fallback" element
section is the correct choice.