You need a small gauge grid on the mandolin to chop up onions, peppers, carrots, celery, mushrooms, garlic & a judicious amount of fresh chilli - I find half a chilli gives warmth not heat.
Fry them off for a bit, then add tomatoes (fresh & chopped, if they are good where you live, good quality tin if not).
Add lentils (dried red or tinned green) or decent veggie mince, a bit of vegetable stock, quite a lot of tomato puree - if you've got an emptyish ketchup bottle rinse it out with the stock & add it. If you're not vegan & have a parmesan rind lying about, chuck that in too.
Whack in some dried basil or oregano. Simmer for an hour or so. If it still tastes a bit lacklustre after all that, IMO Henderson's relish might help.
Disclaimer: this is how I feed the hordes & empty the fridge - categorically no claims made for authenticity. Bears absolutely no relationship to a proper bolognese!