I had to figure it out from scratch and it took a really long time.
I couldn't find a forum, or a thread let a lone how-to instructions really discussing the actual skin customization process in detail. Settings > OSC/Zoom in > Skin Zoom Settings > Set every option to Do not use skin zoom function.
If your Windows custom sizing options (DPI settings) is above 100% then the new 'zoom in skin' feature in v1.6.6.x breaks the clear display of some custom skins, unless you go to Download Skin v1.3: DAUM_PotPlayer_SKIN.zip