Resources will spawn randomly. There are some spots on the map where it's more likely for precious Resources to spawn. (For example the center).
After a long time Resources will disappear automatically (This is indicated by the Resource shrink quickly)
Since there is only a limited amount of one resource-type in the game world, this prevents players from making precious resources inaccessible to others by building a base around them.
There is also a small chance for a resource to turn into a Troll when attacked, dropping 100 of each resource respectively when killed.