You might want to use some reusable greenhouse trays as the season is fast changing. Some ways to do so are to have an unheated greenhouse which can be used to grow greens during the winter. Start warm season annuals, propagate landscape perennials, and shelter-frost tender plants. Besides greens like spinach and lettuce you can grow cold-tolerant veggies such as cabbage and broccoli.
Example of some trays.
Microgreen trays.
Example of some trays.
Microgreen trays.
This one is organic