A description of evolution through variation and natural selection. The part of the process you call "design" is merely a collection algorithms arrived at through previous generations of trial and error, and preserved in the culture.
well...
1. I start by defining the function of the mechanism
2. I then figure out what the mech will have to do to accomplish that function
3. I then whomp up a general large-component assembled design
4. I then break it into sub-assemblies
5. I then figure out how each subassembly is put together, what parts it contains, how subassemblies mate to one another. Basically anything goes at this point - brainstorming, all variations are on the table, promiscuous and complex.
6. Then I sit back and look at the mess I have wrought and ask "ok... how many of these parts can be conglomerated as features of larger, simpler, more robust parts?"
7. then begins the process of simplification, balancing fewest number of components against robustness of the design and what I can actually manufacture/get
8. Then comes trial and error, the process of "whoopsie!" optimization.
so far as I can tell, Nature only performs steps 5 (second sentence) and 8, and does so "blindly" without "designing intent"