How do I stop the construction of buildings so that it will finish on building day of Clash of zone?

You cannot stop the building after it has begun

You cannot pause or stop the progress. The only thing you can try (which has worked for me in the past) is to close the app and not open it until the appropriate time. The building may then only be listed as completed when you open the app and you can get the credit at the right time. YMMV

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