I could take materials in at one end and output finished work at the other, and work would flow in only one direction. Shops come in all shapes and sizes. In my shop the workflow can follow a straight path. Other workflow shapes are possible. A large rectangular room lends itself to circular pattern.
Small spaces are of course more difficult to map a work flow pattern on.
One of the hardest issues is how to leave enough final construction space. You may need to merge one function space with another or even collapse all the functions into one space. These tools are used together and so should be grouped together. Many people argue that stationary power tools in a small shop should be placed on wheels in order to maximize options. I disagree with this advice.