Comment by spekcular

It's tricky. Typically you get thin rods and do each serration individually. Spyderco sells their "Sharpmaker" for this. It's a bit overpriced; you can find decent substitutes elsewhere.

Generally non-serrated edges are preferable unless you have a special requirement, like cutting rope. That yellow Native is part of their "salt" series for people who work on/around boats and water, and hence need to cut rope for sails, etc. Here corrosion resistance is obviously of paramount importance, which is why they use different steels for "salt" knives. There are also plainedge Natives around, for example: https://www.smkw.com/spyderco-native-5-lghtwt-blue-frn.