Housing Block Access
As you can see, a road has been placed on the second square from the housing on the left. Any farming or industrial structure placed next to this road will be provided with labor from the main housing block (Provided there is a city-wide labor surplus, and that structure is not more than 25-33 squares, by road, away from the main housing block). This road can run in any direction or form any shape. Care should be taken to provide these structures with fire and architect protection. Housing can be shielded from negative desirability by a string of shrines as shown.
Another way to provide labor to industry is to take advantage of the fact that when pavillions and bandstands are stacked, they can, if aligned properly, form an access road that is two squares away from occupied housing. This is particularily useful when blocks are paired since it provides an access road directly into the center of the paired blocks. Usually I put Granaries or Storage Yards here, but there is no reason that industry or farming structures couldn't be placed above the block as shown. Architect and Fire services should be provided.