Not the most glamourous part but it is very functional, fast to print (1.5 hour), roomy and blindfolded to place and remove. The total depth is 90 mm, which is the length of the stock spoolholder at the back. Total printing time of the two parts on the X1 is just over 1.5 hour (standard speed and 0.2 layer height). 1 hour for the bucket, ½ hour for the holder. No screws, no glue and no magnets needed.
The "Cup"Holder:
*Update 27 april 2023: Newer models of the X1 (and P1P?) have more ground-clearance (around 7 mm instead of 3ish mm). The V2-version is for the newer model (see picture). Thanks to Chris Sewel for mentioning it and testing it.*
The holder hooks in the plastic frame at the bottom of the printer (it doesn't interfere with the feet). When placed you can slide around your printer as you like, as long as you don't lift it. It is very light, so no stress on the printer when sliding around.
Placing it is simple, tilt the back of the printer a cm, align the right extended edge of the holder with the backplate of the printer, and put the printer down. See photo's. When placed correctly you can rattle it left to right easily and the printer's feet are down as it should.
The Bucket:
The bucket has a generous volume of over 1.5 liters. It is meant to print in spiral or vase mode. Because of that it is fast to print and very light and flexible so it won't rattle. Printed in regular PLA (0.4 mm) it is more than strong enough for its duty. Be careful when removing it from the buildplate. That is, like every vase, the most likely time to damage it (tearing off the bottom when it sticks to much). After that you can throw it around :).
Of course you can design your own bucket, the base is 120x80 mm (122x80.5 no tolerance), with 8mm radius for the two corners).
*Update April 12, 2023: Added a flat and 2 wall thick bucket which has a smoother look. The back wall has a tendency to buckle out after cooling if it's flat, so I added the pattern from the original bucket to the back to keep it straight.*
Happy purging :)