The Solo zone is a massive Overlandzone called Moors of Ykesha, it is the only official solo zone, of course, some will solo atleast parts of the heroic content at some point, but there are no other solo zones than Moors. However, the Moors are really big so thats not much of a issue.
To access it, take the Airship from SS, it leaves where you got all the recent live event quests from the gnomes that dont like monkeys.
Once you get to Moors, you will arrive at the docks, there are several quest npc's, also there are merchants, crafting stations and so on.
Throughout the zone there are several sokokar posts, they work the same way as the rok ones (your rok soko works there, no need to quest for a new one), also there are some other means of travel, not going to spoil those though.
Mobs are almost entirely solo and in the upper 70's and aoe classes will be happy to know that multimob solo encounters are making a return after they went missing with rok. There are some heroics, but either they are on a faction you get through questing so they wont be aggro, or you easily avoid them.
the quests are designed "similar" to the rok ones, as in they are often shortish questlines, introduce you to npc who will hand out next ones. There are various locations where the npc's are, the quests do a good a job at guiding you around though.