I was looking for a simple way to mount my sonic pad to my Ender 3 S1, but didn't want it on the side or hanging off the upper cross member blocking access to the filament spool.

My solution was to mount it to the left of the spool using the self locking mechanism on the stock spool holder.

V3 mounts on the left side of spool holder
V3_RH mounts on the Right side of spool holder

Simply unscrew the stock arms on your Sonic Pad and use the screws to attach it to the spool holder mount. You will need (2) M3 x 10 hex socket head screws to attach the lower mount holes. From there, simply twist it into place on the spool holder

I printed it with the main section horizontal (arms pointing up) with no issues. I used supports for under the arms as they are not 100% parallel with the main body.

If you are comfortable soldering, you might also want to consider wiring up the extra USB connection on the main board. That way you can run it out the bottom of the printer body and not have a USB constantly plugged in the front of your printer. Here is a link https://www.instructables.com/Ender-3-S1-Internal-USB/ (I was able to use the wire from a wired mouse and simply crimped on the appropriately sized pins)

To keep the cables in check I used a bit of fire resistant cable cover for automotive use.