We started reading the wiki page about creating packages first.

Read the guidelines we should follow.

Then we analyze pkgbuilds of others. And finally we copy/paste this code to make our own package.

https://aur.archlinux.org/packages/gnome-meta/

Normally these pkgbuilds follow the rules but you need to check that. That is one of the dangers of copy/paste.

We will create a new package we can now all install with

sudo pacman -S arcolinux-wallpapers-submicron-2560x1440-wqhd-git-meta

General Package Building Information

On the AUR you will find thousands of PKGBUILDS.
You can use their PKGBUILDS or make one yourself.

AUR = Arch User Repository - A user is someone like you and me.

Here are some interesting links if you want to make your own 'recipe' or PKGBUILD.