To dream of large stainless steel thermos flask means:
You have to prepare for cold climate. This has double meaning. Being in a cold climate implies hardship facing the natural elements of weather of the environment. Dream imagery of a large thermos flask means you are storing hot (or warm) liquid for use because you require this. The detail of the dream imagery, like the flask being of stainless steel, suggests basic, rudimentary tool. The surrounding is simple, rustic, rural and only the simplest basics are available. On the other hand, the simple aid may be because the dreamer is unable to afford more costly and complex equipment like an electric thermos flask.
A steel thermos flask is a strong barrier of insulation. It retains its heat, or cold temperatures, for a long time. The exact amount of time depends on the temperature of its environment.
If the dreamer was using the stainless steel thermos flask to keep a hot liquid, then it could be associated with the need for warmth. Consuming a hot liquid is usually cheaper than eating a hot food. This reflects on the financial status of the dreamer. The dreamer could also be in weak health. Drinking a hot liquid helps a frail body, more than drinking a lukewarm or cold liquid.
If the dreamer sees themselves drinking a cold liquid from their flask, it can mean they were hot and needed to cool down. In dreams, being hot can mean anger. Thus, drinking a cool liquid from a flask may cool down a hot temper.