Which Apple Watch Faces Support Modular Large Complications
Start by referring to the Complications sections in the Apple's official watchOS Human Interface Guidelines:


Modular Large - Complications - App Architecture - watchOS - Human Interface Guidelines



  Modular Large
  
  These templates offer a large canvas for displaying up to three rows of content (for example, in the center of the Modular watch face).
  
  


Now if you look through the Watch Faces as available in watchOS 6.1, the following Watch Faces support displaying Modular Large Complications:


Infograph Modular


Modular


Modular Compact