Fancy Block Builder is available on App Lab which is the more experimental part of the Quest store.
Here you can find newer games from smaller developers that have not yet been invited to Meta's holy garden which is the heavily curated Quest store.
Fortunately, installing a game from App Lab to your Quest headset is super easy! No tricks required!
All you have to do is search for the app by its exact name in the companion app ('Oculus' or 'Meta' or whatever they call it these days).