Practice makes perfect, and we should add that to Valheim.
The higher crafting level you have, the better chance of creating a higher level item(this applies to cooking food as well).
crafting one item over and over again would increase mastery(making you have a higher chance of crafting a better version of that item), they are sorted into their categories (spear, axes, swords, shields, armor etc). This would make it so you can't just craft a stone axe over and over again.
| Basic | > | Fine | > | Flawless |
– Standard stats > +2 to every stat > +3 to every stat
+10% durability > +20% durability
> chance do do
elemental damage
Source: https://www.reddit.com/r/valheim/comments/pz2hme/item_qualitycrafting/