If you do it a couple times the process is easy to remember. A recipe can be written down. If you remember the basics you can make up the recipe as you go and check pH with strips or the zap test (and hope you weren't too heavy on the lye!). Many other basic things are similar. After all, they were inveted/perfected with ancient tech/resources.

There are plenty of other things that would be more difficult make, source, or do. How do you preserve food to modern standards if you don't have canning lids and can't make them, refrigerators don't work (some climates might not matter as much), or a local salt/nitrites source? Fermenting is one way, but doesn't work for everything.