Here's my take on a belt buckle. I added some extra wings on the male sides. It worked really well! I made with PETG with the strong BambuLab profile with the model lying flat, not standing up with .2 layer height, and I always use gyroid infill at 20%, with that many walls there wasn't a lot of infill. You might want to put some supports, although I bridged it without any issues - your milage might vary.
I've added a 1.1 version to round a corner that I was always hitting....