Select Storyboard for Interface.

Select UIKit App Delegate for Life Cycle.

Select the same language as your original target for Language.

(In other words, to simplify the setup,
don’t create a Swift App Clip target for
an Objective-C main target, and vice versa.)

2.4

In the following dialog,
activate the new scheme for the new target.

Step 3 - Remove unneeded files

3.1

In the Project Navigator, in the newly created App Clip group,
delete everything except Info.plist and
<app clip target>.entitlements.

Tip:
  For add-to-app users, it’s up to the reader to decide
  how much of this template to keep to invoke
  FlutterViewController or FlutterEngine APIs
  from this code later.

Move files to trash.

3.2