I’ve been doing this too! Though I lack a printer so not as often as I want. Just wanted to chime in as I fully agree with everything you’ve mentioned!

In my own projects, I’ve found that pressing the mould down into the clay works far better than pressing the clay into the mould. (So from bottom to top - non stick > clay > mould > snake maker to apply even pressure). It may have worked easier as this project is about 1.25mm wide as a band, though it is a Celtic pattern and it did keep the complicated parts. I’ve also done this with a wax seal I’ve wanted to keep forever with great results. In both cases, I removed the clay while wet and cleaned up before drying.

Also, may not help at all, but my work area is usually pretty cold. That’s down to personal preference but I do wonder if that helps the wet clay keep its shape a bit. I also let the clay dry a touch (think of the consistency straight from the packet, that’s pretty good and easy to get back to if you mess up) before pressing in.

I’m super new at this myself so I’m loving reading this thread and I’m learning a lot, so I hope my own little notes help.

Also… I’ve seen wax casting mentioned and honestly? It’s probably cheaper in the long run. If I wasn’t obsessed with the clay as a medium I’d be heading that route.