This episode is the wax seals primer.  

Intaglio seals are cut into the surface of the matrix.  Intaglio seals are most commonly used for wax seals and create a design in raised relief in the wax. 

Relief seals have designs that are above the surface of the matrix.  Relief seals are commonly set behind a piece of paper for embossing that also creates a raised relief design.  If a relief seal is used in wax it creates an impressed design more like a mold.  

Catherine Craft Supply

Dexter Rings

Regnas Rings

Letterlocking

http://brienne.org/exhibit-4

http://letterlocking.org/about

https://www.atlasobscura.com/articles/what-did-people-do-before-envelopes-letterlocking

My personal favorite method is to use wax beads in a wax furnace to heat the spoon with the wax in it and the spoon gives you more control over how the wax is applied to the letter.  Melting wax beads in a spoon also gives you the ability to mix wax colors to add to the character of the seal.

Wax furnace

Non-machinable postage 

And a few links from the Wax Seals Revisited Episode

https://backtozero.co/

https://www.letterseals.com/

https://www.carolinapencompany.com/custom-wax-seal

https://vanness1938.com/collections/wax-seals

J.Herbin Wax seal ink pads

Global Solutions Metallic White Shimmer Stamp Pad

Stick wax

Glue gun wax - especially clear wax

Wax beads