DO you mean KISS or KISS A**
Another simplification I've been thinking about
: there is a cut on each side of the first set of fins (set#1, psychadelic orange). These channels could be cut with the cutting wheels, leaving a curved pattern in the center, instead of going back with a 1 mm endmill, to cut it out.
It would make some weird kind of pyramid, about 5 mm high, and would optimize flow at that point.
The 1 mm endmill will still be needed, to finish the other channel junctions.
Searching for "silicone gasket"...