The trim on the tiny house will be 5 inch boards that will overlap the lapstrake siding. To make the trim fit well, first we need to setup the underplaying components.
For the 5 inch trim to lay flat, it needs to be raised to the level of the siding. To do this, a lower layer needs to be placed in the gap between the siding and the edges. This thin board is the thickness of the siding, and provides a flush surface for the 5 inch trim boards.
As you can imagine, this means that all the trim work needs to be done twice. Once for the 3 inch and once for the 5 inch.
The trim needs to line every window and door, as well as finish off the edges of the siding. It is rather time consuming, but it is not the most difficult job in the process. Perfection is not needed as all of these boards will be covered by the 5 inch, all you need to do is make everything become flush.