My coldest weather setup(tested down to -1F this year) is as follows:

SmartWool Socks
+
Cabela's Thinsulate-lined Gore-Tex OverSocks (above ~20F, I substitute Gore BikeWear *unlined* Gore-Tex OverSocks)
+
Thick-soled Shimano SPD Sandals (old two strap style)
+
Size 12 old style Performance Neoprene/Fleece Booties (over my size 10 feet)