How do i delete remnant build product of Xcode project?

The built product is usually in Derived data folder of Xcode. The default is ~/Library/Developer/Xcode/DerivedData.

It can be found in Xcode preferences > Locations > Locations > Derived Data.

It can also be found from the my_project.xcodeproj > File menu > Project settings > Derived Data.

https://help.apple.com/xcode/mac/11.4/#/deva52afe8a4