How to wrap a beamerposter document in frame and columns

Question

I'm trying to create a poster using beamerposter. When doing this, the entire document consists of a single frame and several columns. I would like to avoid having to do this:

\begin{document}
    \begin{frame}
        \begin{columns}[t]
            \begin{column}{0.325\paperwidth}
                ...
            \end{column}
            ...
        \end{columns}
    \end{frame}
\end{document}

And would like to set things up in the preamble/style file so that I can do this:

\begin{document}
    \begin{column}{0.325\paperwidth}
        ...
    \end{column}
    ...
\end{document}

I've been able to wrap the entire document in a frame environment using the code from here, but trying to add the columns environment causes the error File ended while scanning use of \frame.

Here's what isn't working, which is a seemingly minimal extension of the logic of the code at the link above:

\documentclass{beamer}

\usepackage{etoolbox}
\AfterEndPreamble{\begin{frame}\begin{columns}[t]}
\let\myenddocument\enddocument
\def\enddocument{\end{columns}\end{frame}\myenddocument}

\begin{document}
    \begin{column}{0.5\textwidth}
        test
    \end{column}
\end{document}

Removing the columns stuff from the preamble and adding it inside the document works:

\documentclass{beamer}

\usepackage{etoolbox}
\AfterEndPreamble{\begin{frame}}
\let\myenddocument\enddocument
\def\enddocument{\end{frame}\myenddocument}

\begin{document}
    \begin{columns}[t]
        \begin{column}{0.5\textwidth}
            test
        \end{column}
    \end{columns}
\end{document}