Physical labor can be spiritual in two ways: by aiding spiritual growth and by helping return the world to spiritual harmony.  Fist, let me say that by "physical labor" I don't just mean physically demanding labor.  Any physical work is what I mean.  Whether it's building an office building or planting a flower garden.  It can even be work that is mostly mental like designing the building or drawing a landscaping plan.  
    If you are designing a building, designing it and building it according to the laws of divine proportion, divine harmony, and divine geometry make that work spiritual as well as material.  Frank Lloyd Wright understood that as did the builders of the great European cathedrals.  In many ancient societies, priests or shaman were always consulted on the construction of new buildings.
    In art, the great masters like DaVinci and Michelangelo understood and used divine proportion and divine harmony in their works.  When I say the many statues and paintings in Greece on my trip last year, it was obvious that those ancient artists understood divine harmony as well.  Not there is anything wrong with modern art that is mostly social commentary, but it isn't spiritual.
    So study divine harmony and divine proportion and let it help you create great work in whatever you do professionally, or as a hobby, and let it also help you and others grow spiritually.