I’d like to use org-mode to create an academic poster like this one
(random example found using Google):

  http://robjhyndman.com/images/PosterInterests_beamer-723x1023.png

As the LaTeX target, I use beamerposter which is basically just a skin
for Beamer:

  https://github.com/deselaers/latex-beamerposter
  https://www.ctan.org/pkg/beamerposter?lang=en

Such a poster typically consists of two columns (or more when landscape
format is used) and blocks stacked inside these columns.  Sometimes, I
also need something more fancy like a block in a column and more columns
inside that block but that’s rare.

What I would like to write in org is something like the following:

#+BEGIN_SRC org
    #+BEAMER: \begin{columns}
    #+BEAMER: \begin{column}{0.48\columnwidth}

    * Introduction
        :PROPERTIES:
        :BEAMER_ENV: block
        :END:
    This poster is about …

    * Design
        :PROPERTIES:
        :BEAMER_ENV: block
        :END:
    To test A we did B.

    #+BEAMER: \end{column}
    #+BEAMER: \begin{column}{0.48\columnwidth}

    * Discussion
        :PROPERTIES:
        :BEAMER_ENV: block
        :END:
    Our ground-breaking results show …

    #+BEAMER: \end{column}
    #+BEAMER: \end{columns}
#+END_SRC

However, this doesn’t work for two reasons:

1.) Org mode ignores that I want blocks and instead uses frame
environments.

2.) The closing \end{frame} macros are misplaced, e.g:

#+BEGIN_SRC latex
    …
    \begin{frame}[label={sec:orgheadline3}]{Discussion}
    Our ground-breaking results show …

    \end{column}
    \end{columns}
    \end{frame}
    …
#+END_SRC

My question: What do I have to do in org to get the desired structure in
Latex?  This structure would be something like the following:

#+BEGIN_SRC latex
    \begin{columns}
    \begin{column}{0.48\columnwidth}
    
    \begin{block}{Introduction}
    This poster is about
    \end{block}

    \begin{block}{Design}
    To test A we did B.
    \end{block}

    \end{column}
    …
#+END_SRC

Posters really are the only type of document that has consistently
resisted being taken over by org-mode.  So I would be great to have a
solution for this.
  
  Titus