Clinker is a method of constructing hulls of boats by fixing wooden planks so that the planks overlap along their edges. The overlapping joint is called a land. If the plank is too short for the hull, it would be necessary to extend the plank by joining with another piece of wood (xxx joints are common). Planks are also known as strakes (rubbing strake for example) so this method is also known as lapstrake.
Using carvel planks to construct a hull is when planks are fixed to frames with their edges butting up against each other. This method of construction produces a smooth hull, however, the seams tend to require caulking (except in the case of very small boats) and generally it is heavier to similarly sized clinker boats. The construction detail does make a strong hull.
Marcus discusses the differences, demonstrated by two boats in his workshop.
No techniques were demonstrated. The conversation with the boat builder, in this case Marcus Lewis, is unscripted and covers a discussion regarding clinker and carvel construction.