• Create a custom page from within the UI module (Use "Dashboard designer" or "Edit pages" under the "Administration" menu) and save it
  • Create a menu itcon for for your page (note you can hide this "menu item" from actually appearing in your menu)
  • Choose "Root - top level" as the "Parent item" so that no menu/toolbar is displayed

To make the page the default page when you log in, you can go to "System settings" -> "UI module" and set the "logged in page" setting to your page's URL.