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.
