The iCICLE is a case made specifically for protecting the Apple Pencil from scratches and impact. It matches the simple aesthetic and was heavily inspired by 'Johnny' (https://www.indiegogo.com/projects/johnny-the-apple-pencil-case-design) which unfortunately never got pushed to market.
The case features a male and a female that simply threads together.
The case also features a decorative ring which is glued in place with superglue. The ring can be printed or be cut as a 12 mm length of 16mm OD x 14mm ID stainless steel tube, which optionally can be etched easily (see youtube.com/watch?v=geCVfsAN4Tk&t=2s).
Print the male and female part with the rounded end facing down and use raft and support material. This orientation will result in a cleaner threading. The raft is important for preventing the print from falling over.