I've dragged an old electric kettle out of storage and set it up in the bathroom, I use it solely for filling hot water bottles. This current winter I've been afflicted just about every 2nd day with Raynaud's Syndrome in my feet. The "trick," according to a podiatrist, is not to let the feet go cold in the first place. Easier said than done.
I place a folded hand towel on the cold floor with a single thermal sock on it. Then I add a two-litre hot waster bottle containing 600ml of 80ºC water. The soles of both feet rest on this bottle.
I then lay another folded hand towel and a second thermal sock over the top of my feet topped with a 2nd similarly-filled hot water bottle. This keeps the feet warm enough for several hours.
The podiatrist recommended wearing thin socks underneath the thermal socks once the hot water bottles have done their job.