I needed a buckle for a project using 25mm wide webbing that is 2mm thick, and found onethou's project which worked perfectly and required minimal post processing.

My modification is still a little wide for 25mm webbing, so any webbing you use will probably have a couple mm to wiggle, but just like the original, it cinches tightly and closes securely.

Here's a link to onethou's assembly video: https://youtu.be/WFBYDQT83NA