% \usetikzlibrary{calc,trees,positioning,arrows,chains,shapes.geometric,%
% decorations.pathreplacing,decorations.pathmorphing,shapes,%
% matrix,shapes.symbols,plotmarks,decorations.markings,shadows,backgrounds}


\newcommand{\scale}{.65}

\begin{tikzpicture}[auto, on grid, scale=\scale,every node/.style={scale=\scale} ]

\tikzstyle{CTU}=[draw, text centered, minimum size=1cm,anchor=south west]
\tikzstyle{Tile}=[draw, line width=1.5pt]
\tikzstyle{TileLabel}=[text centered,fill=white,inner sep=0,font=\large]

% \newcounter{maincounter}

\setcounter{maincounter}{1}
\foreach \x in {1,4,7}
{
  \node[TileLabel]  at  (\x + .5,1.5cm) {Tile \#\themaincounter};
  \addtocounter{maincounter}{1}
}

\setcounter{maincounter}{1}
\foreach \y in {0,-1,...,-8}
\foreach \x in {0,1,2}
{
  \node[CTU]  at  (\x,\y) {\themaincounter};
  \addtocounter{maincounter}{1}
}
\foreach \y in {0,-1,...,-8}
\foreach \x in {3,4,5}
{
  \node[CTU]  at  (\x,\y) {\themaincounter};
  \addtocounter{maincounter}{1}
}
\foreach \y in {0,-1,...,-8}
\foreach \x in {6,7,8}
{
  \node[CTU]  at  (\x,\y) {\themaincounter};
  \addtocounter{maincounter}{1}
}

\path[Tile] (3,1) -- ++(0,-9);
\path[Tile] (6,1) -- ++(0,-9);

\draw[draw=red,densely dashed,black!70!green] (-.1,1+.1) rectangle (9.1,-8-.1);
\node[TileLabel]  at  (9/2,-8.5) {Slice \#1};

\draw[white] (-.4,2) rectangle (9.4,-9);

\end{tikzpicture}