Can I reserve a page defined during the document for the appendices?

Question

I have a simplified slideshow class that basically creates each slide as a new page within an article class document. I'd like to add the ability to define a slide as a "pocket slide", a slide whose content should go in the middle of the document, but will only be presented if questions are asked. As such, I'd like to define the slide in the middle of the document, but have the slide go at the end. Can anybody give a suggestion for a package/mechanism to "reserve" pages for later?

Example:

\documentclass[english,20pt]{puslides}
\begin{document}
\titleslide{Some Title Here}
\onecolumnslide{Introduction Content}
\onecolumnslide{Parenthetical Content}
\onecolumnslide{Conclusions}
\end{document}

And the output would be a slideshow in this order:

+------------+     +----------+      +-------------+     +---------------+
|            |     |          |      |             |     |               |
|            |     |          |      |             |     |               |
|    Title   +---->+  Intro   +----->+ Conclusions +---->+ Parenthetical |
|            |     |          |      |             |     |               |
|            |     |          |      |             |     |               |
+------------+     +----------+      +-------------+     +---------------+

Answer 1

Without your actual slide maker, I just show the basic concept, using \g@addto@macro to append content to an existing \def, which can be recalled at the end.

\documentclass{article}
\makeatletter
\def\pocketslides{}
\newcommand\savepocketslide[1]{\g@addto@macro\pocketslides{#1}}
\makeatother
\newcommand\titleslide[1]{TITLE: #1\clearpage}
\newcommand\onecolumnslide[1]{ONECOLUMNSLIDE: #1\clearpage}
\begin{document}
\titleslide{Some Title Here}
\savepocketslide{\onecolumnslide{Parenthetical Content}}
\onecolumnslide{Introduction Content}
\savepocketslide{\onecolumnslide{More Parenthetical Content}}
\onecolumnslide{Conclusions}
\pocketslides
\end{document}