On this guitar I started with the segmented backstrip. Here are a few pictures that show a little bit of the process. I do all my inlay work by hand without a CNC machine.
After designing the inlay (which took me almost two days as I just couldn't decide what compliments the wood best) I route the channel for it.
The next step is to square out the corners. I use chisels and scalpels for this job.
Then the inlay gets fit and glued in.