I'm on Developer branch, so maybe it's different in the "normal" version.
When you open the start page, on the upper right corner you have a config button. Among other options there was "Speed Dial" check box. Is that what you wanted?
So I have a dropdown that shows me my open tabs (presumably not what you're talking about) in the upper right corner of the window.
A cog which lets me 'Customise start page' but expanding Navigation and unchecking Speed Dial did not disable speed dial.
On the top left I have a Menu but the only thing I can see to do with speed dial is a button which opens it in a new tab or focuses a tab which already has it open.
I really just want a blank page when I open a new tab.
When you open the start page, on the upper right corner you have a config button. Among other options there was "Speed Dial" check box. Is that what you wanted?