I would love to know how to do more intricate details like this on a leather, the feathers look amazing!

I honestly couldn't tell ya, though I suspect that it might actually be a relief carving on a thicker piece of leather given how it's raised up around the surrounding leather, though there is also no seam I can see and no tooling marks to indicate that the rest had been trimmed down.

So! Leather is one of those fantastic materials that, when wet, is extremely malleable, and once it dries it retains that shape pretty well. You can hammer little stamps into wet leather to dimple it, and it will keep that dimple. This is the a lot of delicate tooling work, most of which involves simply tapping the stamp with a mallet to press the leather down. Whoever tooled this is quite skilled.

I know this much, I've had tooled leather before. In this case though, the leather is actually raised over the surrounding leather, and its very clear that the tooling has been carved in several places. when you look at the image itself. its not just stamped, though it is stamp embossed around the perimiter. The image itself is about 3 mm above the surrounding leather. And on the backside of this wallet there's no dimpling to indicate that it was hammered from the back to give the raise either.