OK. Roughly:
Cube a butternut squash, roast in olive oil.
Meanwhile, fry onion, garlic with a bit of dried chilli flakes and a cube of grated ginger in some oil in a big pan. Cumin seeds can also be a nice addition if you like them.
Stir in the dried red lentils and heat through a bit.
Add the roasted squash, stir round, add 1-2 pints of weak bouillon (such as Marigold) and simmer for 30 mins or so.
Sometimes I also put a tin of chopped tomatoes in as well.
Sweet Potato variation:
As above but with sweet potato instead of squash, and coconut milk instead of tinned tomatoes/stock. It is equally lush.
I imagine both could be done in a slow cooker.