The truth is that all you need to do is have at least a few posts with featured images. Then you have to play around with the theme settings, such as selecting featured posts as the content source for the slider and your website layout will be built automatically.
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I should have been more detailed: how do I create this effect?
In the theme settings (of the portofolio theme) I see the possibility to remove the left column under “post page” (“This option sets all posts to the alternate template layout, permanently removing the left column”). But I’ve only ever seen one column, never encountered a “left” or otherwise column.