There's nothing difficult here and yes it's cutting saw + CNC. No problem because fins aren't tall (~2mm). But here is a 0.25 mm version with ~8 mm copper fins using cutting saw too from a polish friend and no problems (so little bent) :
Another technic said by BB2K is the wire EDM I used to do minichannels from 0.5 to 0.25 mm too without constraints :
You've got the choice to make such design...