Installing Legrand on-wall electrical conduit in older masonry unit

Installing interior on-wall electrical conduit to add a new outlet under a window in a 1940s masonry building.
Legrand materials used:
NMW2 Starter box for existing outlet: www.amazon.com...
NMW2-D box for new outlet: www.amazon.com...
Inside elbow: www.amazon.com...
Flat elbow pair: www.amazon.com...
NMW1 Plastic wire channel - 5 feet, 2 pack: www.amazon.com...
Non metallic coupler and wireholder - (not necessary for shorter runs like mine): www.amazon.com...