In 2009, I made a trio of seat lugs. They were intended for a batch of Dutch bikes that remain not much more than an idea.
The way one makes these things is silly, but it offers the designer considerable creative freedom. You essentially build the joint twice, and carve a lug in between. I made these when my file handling was at its zenith, which is both worth noting (file handling is underrated) and also a totally silly skill to possess.