Muck has evolved quite a lot over the last couple of months. It’s developed and published by a single developer which is quite impressive. That developer is Dani, who also has a YouTube channel. In any case, you can tell that it’s developed by one developer though. Some things in this game are pretty complex, and players do run into roadblocks pretty often. One would be making flax fibers.
How To Make Flax Fibers in Muck
The reason for the confusion for many crafting items in Muck is the fact that recipes are learned upon getting a particular item for the first time, i.e. the item or items needed to craft that particular item.

So, following the general theme, you first have to find flax, in order to start crafting flax fibers. Point is, the system for learning crafting recipes is a bit unorthodox, but still, I would cut Dani some slack.
Well, if you need to find flax to learn the flax fibers recipe, where do you get it?
This is quite a difficult question to answer. Mostly, flax can be found near or in wheat fields. That shouldn’t always be the case, but players have reported that the highest chance of finding it, is near wheat fields.
IMPORTANT: Flax is a flower. It is a blue flower with a yellow dot in the middle. It is pretty hard to miss, but it is small, so look for it closely on the ground.
After you collect some flax, you’ll need to make a fletching table, or use one that you already have.
Click on the fletching table, and then navigate to Miscellaneous or Misc for short. You should see flax fibers here as an option to craft, albeit, if you have collected enough flax.
One flax flower will equal one flax fiber. At the moment, I believe that flax only has a couple of usages, one being a strong armor. It is unclear whether more items will require flax fibers in the future, but it is highly likely.
Make sure to scout the whole area after finding one flax flower, as they do tend to spawn in groups near those wheat fields.