Adding a delay as part of a workflow isn't currently available in Flow. It's a feature we hope to add in an upcoming release of the app.
As confirmed by @joshbeckman, this is currently not possible to implement within Shopify. If you are looking for a third-party solution, I recommend checking out the Arigato Automation app. With the delay functionality, sending out scheduled follow-up emails is possible after an order is raised. Here's a sample workflow from the app's library.
would you mind checking our app Payster: https://apps.shopify.com/payster-payment-email-reminder
It's designed to send email reminders to pay for pending orders but can be easily used to send an email to customers after an order is created. The setup is straightforward and fast.
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This is doable with our app Mechanic