Force a beamercolorbox to the bottom of a frame with no margin

I would like to occasionally put some notes at the bottom of a frame using a beamercolorbox. I am trying to force this box to be exactly at the bottom, without any blank space before the end of the frame.

I am currently using this code:

setbeamertemplate{footline}{}
% ...
vskip0pt plus 1filll
begin{beamercolorbox}[sep=6pt,center,wd=paperwidth]{block body}
Text
end{beamercolorbox}

However the result looks like this (you can note some extra white space between the box and the end of the frame):

I have removed any content from the footline. Actually I’d also be happy with the box overlapping with the footline, as I use it for the frame number only and I could adjust the padding in the box to avoid the text to overlap.

Thanks in advance for any suggestion!

newcommandbottomtext[1]{
begin{tikzpicture}[remember picture,overlay]
node[inner sep=0pt,outer sep=0pt,anchor=south] at ([yshift=0pt]current page.south)
{begin{beamercolorbox}[wd=paperwidth,ht=3ex,dp=2ex,center]{block body}
hfillparbox[c][7ex][c]{0.8paperwidth}{footnotesize#1}hfillnull
end{beamercolorbox}
};
end{tikzpicture}%
}
%...
bottomtext{Text goes here}