In Path of Exile, Elder can control at most 30 maps, he always controls a single connected area, Guardians and Elder can not unspawn so the last connection between them stays under Elder influence when completed, Shaper can only attack Elder maps from adjacent maps he controls. Bear in mind that enough poe orbs is essential. How to make a setup on your maps?
1. Get Elder to spawn on a map with less than 4 connections. This is to ensure that you can cut the direct connection between elder and one of his guardians after forming the ring. If you are lucky they occupy important chokepoints. Depending on where they spawn it should be possible to make a ring that doesnt't span the entire map but only one or two quadrants. In any case you should make sure to plan out both your route for closing the ring and your final atlas in advance. You don't want to discover that something doesn't work out after 100 maps.
2. Closing the ring. You can't just run the maps you want in your final version of the atlas since Shaper will cut you off a long time before the ring gets closed. Since Elder and Guardians can't unspawn, it doesn't matter which "half" is bigger. When Shaper gets a chokepoint he can cut off 20+ maps at once. Because of this it is important to cover all connections.
3. Cleaning up. Now that all connections are safe, you can start moving towards your final setup. If you want it to be untouchable. There must be a single path between endpoints, otherwise shaper can take one of the maps. If there are some maps you want perma Elder on the path has to go through that map. All "leftover" elder maps (up to the cap of 30) have to be completely surrounded by elder territory so they can't be attacked by Shaper. When filling up a corner for this you have to make sure that you don't open up a second path or Shaper can take some map away.
When you have your final Atlas planned out you can start shaping your Elder territory. Note that when you replace one path between waypoints with another you need enough "free" elder maps for both until the new path is connected so plan ahead.
Unlike buy poe currency, it can be tricky to get the last few elder maps where they are supposed to be and you also need some luck. Until everything is completed Shaper and Elder can still screw you over. If you just want to run your favourite map on perma Elder you don't strictly need perfection. As long as elder doesn't enough free space to open up new paths (clearing them could mess with your sextant setup) it should be fine.