This is my take for a housing of a 5-Slider volume mixer.

How to build:

all the parts pretty much stick together by their own. I just hot-glued the Arduino in place as seen in the pictures.

I included the slider-caps as seen on the pictures as well as blank ones for you to modify for your own needs.

if you use the dupont / jumper cables you need to bend some of the Arduino pins for clearance. If you solder directly to the Arduino ther should be no problems.

Parts i used:

Slider: https://de.aliexpress.com/item/1005004247227671.html?spm=a2g0o.order_list.order_list_main.19.59035c5f1nmGxl&gatewayAdapt=glo2deu

Arduino: https://de.aliexpress.com/item/1005006053215107.html?spm=a2g0o.order_list.order_list_main.13.59035c5f1nmGxl&gatewayAdapt=glo2deu

and some cables.

For the Software take look at: https://github.com/omriharel/deej