This side panel will boost Wi-Fi signal a fair bit by keeping the antenna module from laying flat on metallic surface. It still gives worse signal than using Compute Module 4 Antenna Kit externally and only provides moderate improvement from the default antenna placement which made it good enough for my needs.
Make sure to set your Raspberry Pi to use external antenna if you haven't done so yet by putting dtparam=ant2 into config.txt.
The author marked this model as their own original creation.