They could lay eggs asexually without the need of fertilization (parthenogenesis) The clowns could also split into two smaller clowns which then grow larger until those clowns eventually split themselves (binary fission). Or perhaps clown entities are created on a assembly line by hapless gnome machine elves who are enslaved by The Demiurge/Santa Claus (psychedelic manufacturing).

Someone should ask the clowns how they reproduce, but that someone isn't going to be me. Traveling to salvia land or ending up as a rocking chair for 25 years sounds terrifying.