Prusa3D Core One assembled from kit ( https://www.prusa3d.com/product/prusa-core-one-kit/ ) in roughly 36 hours, including 5 hours of sleep and frequent toddler-herding
Quite fun and satisfying
I did make a few mistakes, but wholly my own, and avoidable by reading the actual instructions
Benchy test print (15 minutes) is complete, so I guess I can start planning holiday show-bag gifts for nieces and nephews
I worked for a small print farm doing printer maintenance, and that included building several Prusa Mk3s. I got it down to about 6 hours.