I use lake 302 winter boots with good results by themselves down to about 25 F.

If I need more protection I use plastic bags (2-4 per foot depending on how cold and how much wind) on the outside of the boot held in place with rubber bands. This works really well, is cheap, and they are recyclable.

When conditions get worse I use my Neo Overshoes that I insert my Lake 302 boots into (now wearing 2 pair of boots).

When the worst conditions are are here I use the Lake winter boots, Neo Overshoes and turn my Hotronics foots warmers on that are already installed in my Lake Boots. My feet are always warm in any conditions!