The secret to warm feet is to keep your bodies core warm (internal organs and brain). If your core temperature drops your body naturally starts to reduce blood flow to the extremities in order to keep the core warmer. Once that happens no amount of insulation on your feet is going to help. If your core is warm then your body sends more blood to the extremities in order to cool down the core. If your feet are getting cold you need a warmer hat and coat.
Another tip is to increase your bodies metabolism while on stand. Eating high energy snacks while sitting still and doing isometric exercises which require no movement will really ramp up metabolism and blood flow. I admit, I don't see sub zero temps often, but I hunt quite often with temps in the teens and single digits are not uncommon. I haven't owned a pair of insulated boots in at least 20 years. One or 2 pairs of good quality wool socks in my boots have always been enough,
