[xmonad] How to make a window floating above all the other windows and border-less?

[Magicloud Magiclouds]

Hi,
  I felt that a digital watch at the corner was so in-noticable. So I
planned making a clock watch, just three handles, transparent
background, in the center of the screen, floating.
  But I met a few problems here. I made the windows "over-redirect",
so it has no border. Well, how to make it floating above all the
others then?
  Normally, I could do this in xmonad's config file, to make THE
window floating, which also is above all the other windows. But with
"over-redirect", it does not work....

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