When in the scan to USB/Network scan options go to Layout > Book Scanning.
There are multiple settings to choose from, if your not scanning a book just tell it to do one page only and for each pass of the light touch the Next Original option. When it completes the scan of the page it will ask you to scan the next one, just keep loading originals and hit the Start button. You should be able to get it to do what you want within a couple of tries.
Just remember to set the original size manually ala Layout Adjustment > Original Size because the printer will only detect industry standard sizes via Auto.
The printer is incapable of scanning when you place paper on the glass, it has no way of knowing the paper is there and even if it did would not know what you wanted to do with it so pushing the Start button is the only way to scan the next page.