%%
%% The LaTeX Companion, 3ed
%%
%% Example 8-4-28 on page I-630 in "Poster applications".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{159.0pt}

%StartShownPreambleCommands
\usepackage[poster]{tcolorbox}
%StopShownPreambleCommands

\begin{document}
\begin{tcbposter}[
    poster = {columns=5,rows=4, % set up raster
      spacing=1mm,              % spacing between elements
      width=140pt,height=120pt, %  - normally not needed
      showframe},               % and show it
    boxes = {sharp corners=downhill,colframe=blue} ]
% content boxes ...
  \posterbox[colback=blue!20]
            {name=title,column=1,span=3,row=1}{}
 \posterbox{name=graphic,column=4,span=2,
            row=1,rowspan=1.5}{}
\end{tcbposter}
\end{document}