Today's technique is a simple yet very useful and effective one by Sandy Cash on Flickr. You can check out her post here: https://www.flickr.com/photos/sandy_cash/3871984489/in/gallery-37217189@N04-72157633532233362/
The 1x4 arch brick that is used unfortunately only comes in that form, unlike many slopes which also come inverted. This means that trying to create a perfect circular window is hard, or at least was.
This technique utilizes the headlight brick, which when laid flat is equal to 2 plates in height. This coupled with the 1x1 modified plate with ring allows the 1x4 arch to be positioned upside down, and it looks great below the same piece attached normally. This creates the perfect circle that can be used for windows such as portholes on ships.