You need parts for plastic plants (aquarium plants suit really well) or dried real plants, caps and hot glue.
When you use black hot glue to put the flowers into the pot, you get to make the soil at the same time. You can also use another glue and sprinkle the dried coffee grounds on the surface.
Many caps are useful as pots, for example the brown pots in the picture are the caps of toothpaste tubes, caps of essential oil bottles, hairspray bottles and gas bottles for a carbonation machine, painted with nail polish.