While the "Building" progress bar is shown, your project is still being created:

Depending on the project settings you selected, it can take some time to complete. The progress bar is only a rough estimate. If you are trying to build many projects at the same time, some projects could also take longer to build. When the project is ready, it is shown as below:

If you selected to be notified on slack, you should receive a notification when the infrastructure is ready. The activity stream also shows:

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