Sometimes what causes your feet to get cold is that they were warm in the first place, so they sweated. Now you are walking around in damp cold socks. There are a couple things you can try to mitigate this:

• Wool is warmer when wet than Cotton. Wool socks can come in a variety of cushion/warmth levels, so you can pick what works for you.
• Sock liners are a thin sock to wear under your normal socks. They are usually made of synthetic fabrics that wick the sweat away from your feet to the outer sock so your feet don’t feel wet. They can also help with chafing and are usually used for outdoorsing or sports.
• Wear breathable shoes as long as you aren’t walking somewhere too cold and wet. When your socks can dry out your feet will feel warmer
• Wearing slippers alone can end up both sweaty and drafty. Wearing socks with your slippers can keep your ankles warm and reduce how drafty they feel, but the draftiness of the slipper can also help to keep your socks dry.
• Take off your shoes or slippers periodically to let your socks dry out.
• Feel free to change your socks whenever you want. There is no rule that says you have to wear the same pair all day.

This may also sound counterintuitive, but put on a sweater or vest. When your core is more exposed, your body will reduce circulation to your extremities to keep the heat in your core. If you insulate your core, your body will increase circulation to push the heat to your extremities to keep your core cool.

Lastly, get a good night’s rest. Thermoregulation is one of the things that will suffer for lack of sleep.

You say non-electric, but since battery tech has improved drastically over the last decade, battery powered warming socks are much more useful today.

Also, a major key to keeping feet warm are good socks (wool/synthetic mix are excellent), and shoes that are comfortably spacious with your thickest socks. Tight fit, even just snug, will make for cold feet.

I use cotton socks with some Bombas wool slippers on top. Feet stay dry and warm.

Normal, layered socks don't work for me either, but that combo seems to do the trick.

Moving and alcohol both help to increase blood flow in the feet to keep them warm.

Fuzzy socks!! I have multiple pairs of thermal socks that are fuzzy on the inside. I love them so much. Highly recommend.

We have some heat holders that work pretty well, if you want to start toasty we stand on the heater vent first

Honestly invest in good slippers. I got these before COVID and they are hands down one of the best investments ever. since I work from home I just wear them all day. Do they make me look like a geezer, yes. But my feet are cozy.

Try compression socks as the innermost-layer, which are long enough to run up the calf. With these on, I use one more layer of regular cotton sock and generally feel pretty warm (compared to just thick wool socks, or multiple other layers).

Indoors or outdoors?

I've lived in Snoozies in winter for years. Wearing a pair right now, actually. I'm not going to go outside in them, but for indoor use, they're less restrictive than socks or slippers, while being a nice way to raise the temp by several degrees.

I like good quality wool socks. Smart wool is my favorite brand, but there are a lot of good ones out there. I use their hiking socks very frequently

Alpaca fur socks help.

Throw on some toe socks and have a hot bath.

in addition to what's been said, keeping yourself hydrated helps with circulating heat and you can always have a hot beverage to help yourself get hydrated and warm up! (try broth / lightly salted warm water; caffeinated or sugary beverages tend to have the opposite effect, although it might work for you!)