Potter wasp (Ancistrocerus sp.) constructing nest cell.

As you can see this wasp is indeed making a pot, one mouthful of mud at a time, that will eventually house a single larvae with a provision of paralyzed caterpillars.
An interesting observation is that only the larvae feed on other insects, adults solely run on nectar. The transition from carnivore to vegetarian a matter of dietary requirements at the time. The larvae using animal proteins to develop, while the adults are fueled just on plant sugars.

Photographed in Ontario, September 2020.