A quick breakdown of Armament Haki levels:
- Basic – Harden the skin
- Intermediate – Flow Haki outside the body
- Advanced – Penetrate others with Haki and cause internal destruction
A maser canon is an electromagnetic weapon. A maser is electromagnetism.
So in short, Kid will create a magnetic field that will act as a foundation for Conqueror’s Haki to be coated on top of, this will essentially be the replacement for the Advanced Armament Haki.
Furthermore, I believe Whitebeard had a similar approach where he used a quake bubble as the foundation. This will also be an interesting parallel with Kid being the next Whitebeard and Luffy being Roger.