Simple to print.
The posts' design diameter is 7.96mm and the corresponding holes' design size 8mm. I cleaned the holes with a 1:50 tapered reamer.
As PLA is rather grabby, to achieve full motion as shown in the video, I found it necessary to lubricate the slides. I used Olive oil. There may well be better lubricants, but it works fine.
Three of the posts have holes in them sized to take 3mm screws in conjunction with the washers. An optional extra!