How to make flower pots?
You can use Portland Cement: Google Search link
How to make plaster of paris flower pots:
Try looking up hypertufa instead of using cement or plaster.
These are cute! https://www.homelovr.com/diy-succulent-planter-ideas/
If you want cheap flower pots, some of the garden centres or gardeners may give them to you for free (Basic Plastic) which you could decorate to taste.......