It's not anything fancy! I usually use what I have in the fridge so I'll sauté one chopped onion in some Olive oil and garlic, spring onion if it's all I have.
While that's going I chop my veg last time i used zuchinni, carrot, sweet potato, potato, capsicum, squash, broccoli, fresh tomato, leek but really whatever is in the fridge. I throw the veg into the slow cooker, add the onions, usually a tin of lentils or chickpeas, and one or two tins of chopped tomatoes. Then I add in maybe half a cup of stock, or more if I need it (slow cooker is generally overflowing by now) salt and pepper and cook it all day. I keep stiring it during the day and I'll add some salt, some onion powder and a shake of turmeric and cumin powder. Really just whatever taste you prefer.
You can also just cook it on a pot on the stove. When it's done we have it over brown rice or on its own with Greek yoghurt or sour cream on top. I take a few big scoops and throw it in the nutribullet and blend, then I use that as pasta sauce and add cheese for my 3 year old, it's really flavourful and I feel like he's at least getting some veg! The rest i freeze in small portions of sauce for him. It's got quite a tomato flavour when blended.