Because the LED Strip Holder design I made doesn't have any way to register one to another. So to solve that, I made a jig that just slots on top and aligns them.
To use the jig:
Screw in one track
Place the next track next to the previous
Place the jig on both tracks and align them
Screw in the second track
Repeat until you are done
You may want to sand the inside walls to make sure they are flat