You should be able to install evilwm and conky using apt.

https://wiki.archlinux.org/title/Evilwm

Outside of the install step (you’ll use apt to install), the setup instructions are the same.

Inside of evilwm you can manually launch conky from a terminal (ctrl alt enter to open a terminal), or if you want it to start automatically you can add it to the .xinitrc (https://wiki.archlinux.org/title/Xinit).

Evilwm has a configuration file where you can set window configuration on a per app basis (so if you wanted it as part of the background layer, or in a fixed window location.