Add all of the ingredients (through the red pepper flakes) to the slow cooker and stir to combine. Cover and place on high for 4 hours or low for 8 hours.
Remove the lid and add the basil. Taste and adjust the seasonings as needed (see notes).
Bring a large pot of water to a boil. Add the pasta and cook according to the package instructions.
To serve, add pasta to each plate and top with the lentil bolognese. Add more fresh basil and vegan parmesan.
Video
Notes
I would avoid using red lentils - they will likely turn to mush in the slow cooker.
If the sauce is too thick after it cooks, add more broth or water. I added about 1/2 cup more broth.