As the name suggests a building designer designs buildings. This is an involved process as many design criteria need to be taken into account during the building designing process.
The first step is identifying building designers who would like to work with, you should then reach out to each of these designers stating your intentions and see if they are happy to work within your requirements, you can then shortlist and hire a building designer.
It is important to get the design of your building right to take advantage of the land you have, the aspect of it, the natural conditions are around the building. By considering these elements you can have a building that fits naturally within its environment.