How to delete photos from iPhone but not from iCloud

Macworld
If you are running out of space on your iPhone you may be looking at the huge amount of space being attributed to Photos and thinking that deleting all the photos from your iPhone would be an easy way to increase your storage.
You may have heard of iCloud Photos and wondered if that would be a way to back up your photos so you can delete them from the iPhone. Or you may already be using iCloud Photos and think they are all backed up in iCloud and can be deleted from your iPhone. But you