Autumn Leaves

Does anyone have good ideas re turning my mountains of leaves into good compost for the garden, in the easiest way possible, please?

Currently, they are in the garden bin all alone. Perhaps I should try putting my Bamix into them in order to reduce their apparent volume? No? Oh well, I will continue to scrunch them between my hands because it is making more room.

I once read that they could be put into a large black garbage bag (or 5 of them), weighed down with something or other, left on the garage roof for heat and rain to do their work and after several months I will get good compost. I have no compost bin as not enough room here for one.