I keep a directory called LaTeX inside my home directory. Inside that I keep a file with all my frontmatter, myfrontmatter.sty (technically a package rather than a class), and also my biblatex file and a scan of my signature for signing letters. When I start a new LaTeX document and add the line \usepackage{/home/nanna/LaTeX/myfrontmatter} to the top (note, no .sty). This keeps my frontmatter minimal and tidy.
Inside myfrontmatter.sty:
\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{/home/nanna/LaTeX/myfrontmatter}[2015/01/01 by me]
\RequirePackage{amsmath} % Just replace `usepackage` with `RequirePackage`
\RequirePackage{amsthm}
...
\addbibresource{/home/nanna/LaTeX/biblatex.bib}
...
%% Macros like for inserting my signature
\newcommand{\mysignature}{\noindent\includegraphics{/home/nanna/LaTeX/signature.png}}
...
\endinput % Not sure if this line does anything?
And that's it. I never have to worry about a package I've forgotten to add in. Granted a journal might not accept my custom package but I can always just copy and paste it all into my frontmatter, minus the top two lines and replace all the RequirePackages with usepackages.
https://www.overleaf.com/learn/latex/Writing_your_own_packag...
How I do it...
I keep a directory called LaTeX inside my home directory. Inside that I keep a file with all my frontmatter, myfrontmatter.sty (technically a package rather than a class), and also my biblatex file and a scan of my signature for signing letters. When I start a new LaTeX document and add the line \usepackage{/home/nanna/LaTeX/myfrontmatter} to the top (note, no .sty). This keeps my frontmatter minimal and tidy.
Inside myfrontmatter.sty:
And that's it. I never have to worry about a package I've forgotten to add in. Granted a journal might not accept my custom package but I can always just copy and paste it all into my frontmatter, minus the top two lines and replace all the RequirePackages with usepackages.