How do I make sure the Architect is in the right place without destroying my snake?

Continue building your main chain until you get to the golem part and build something like this:
https://sulozor.github.io/#/atziri-temple?t=ACFIIUghSCFIIUhgOWA5YDlgSCE5ADkAOQA5IUgAmAAAABEySCEACAAAAABpIUgACAgICABwSCEAAAAIAAB6IUgAAAAIAHGASCIxOWAIAGkxIg
this will leave your desired location as the only viable place for the architect to move to.

Is that little white blob where you want him? If so he can only go there if there no room connect to there so that golem and garrison cant be there.