Summary

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....

Print Settings

Printer Brand:

Bambu Lab

                                            <p class="detail-setting printer"><strong>Printer: </strong>                     <div><p>Bambu P1S</p></div></p>                                                                                <p class="detail-setting rafts"><strong>Rafts: </strong>                     <div><p>No</p></div></p>                                                                                <p class="detail-setting supports"><strong>Supports: </strong>                     <div><p>Yes</p></div></p>                                                                                <p class="detail-setting resolution"><strong>Resolution: </strong>                     <div><p>.2</p></div></p>                                                                                <p class="detail-setting infill"><strong>Infill: </strong>                     <div><p>20%</p></div></p>

Belt buckle!