Its actually quite simple at its core.
Theres a temple. You can build rooms in it. Rooms connect to each other. Some rooms don't connect to each other. You can look up rooms details online.The more rooms you have, the more multipicative bonuses your temple gets - it becomes harder and more rewarding.
Rooms tend to destabilise (get destroyed) after every run. If you kill architect or Atziri on the run, they destabilise way more. You can get medallions in temple - one of them lets you lock the room so it cant destabilise onthat run. That gets us to the key technique: if you build rooms in a "snake" pattern - meaning you chain them one after another without looping, then the temple cant really destabilise any room "in" the chain - only the last one, because otherwise it would make some rooms not connected to anything. So uf you build a chain and lock the last room, the chain will stay.
Garrisons and spymasters have a high chance to drop lock medallions - you chain a lot of them and that allows you to consistently sustain locks for a giant temple. Thats it.
You can find an online tool to plan your temple. I dont recommend Fubgun's youtube video because it has a lot of mistakes.