How are Jewish cemeteries made? Can they just be expanded?

I went to a Jewish cemetery the other day and I saw that space was scarce. Can a (disregarding local laws) a Jewish cemetery with borders be extended by a plot? Do Jewish cemeteries even have borders? Or can Jews be buried anywhere (by religious law or custom that is)? Are there rules to what land can become a cemetery, does a Rabbi have to “bless” the land or something of the kind (or not)?