Since there are no NPC vendors in New World, you're going to have to get thrifty with your clothes. Here's where you can harvest fibers from hemp plants to craft cloth.
Like most resources in New World, you'll need a tool to gather fibers from hemp. To harvest plants, you need at least a flint sickle equipped on your character.
Hemp can be tricky to track down at first until you know what you're looking for. But when you do find some, it tends to grow in large patches that you can harvest all at once.
Where to find Fibers and Hemp plants in New World
Hemp grows in forested areas across New World.
However, if you run into the undergrowth not knowing what it looks like, it's easy to traipse around in circles.
When gathering hemp, look out for the distinctive purple flowers on the tops of the tall plants. This distinguishes hemp plants from regular and briar bushes.
Kannan Tomb Hemp Fibers
A good place to find hemp fibers early on in New World is almost directly north of Windsward Village.
In the forest around Kannan Tomb, you should be able to find multiple patches of hemp, which will help you know what you're looking out for in other forests in future.
Also, it's worth knowing that Fibers are actually quite heavy, so be sure to deposit any unused items and weapons in your storage before you go foraging.
New World | How to turn Hemp Fibers into Cloth
Once you've collected as many fibers as you can carry, return to a large settlement like Windsward Village.
In the middle of the crafting area, you should find a Loom. Here you can spin the hemp fibers you've found into cloth.
This can then be used at the nearby clothes-making station to fashion light and leather gear. Or you can make your way to the forge and use cloth to pad out your heavy iron armor.
For more resource guides, here's where to find Saltpeter for Gunpowder in New World.