casting delicate unfired clay- what material should i use to make a mould?

i am experimenting with small 3d roses made of clay {on a base of clay} which i want to cast and make into latex roses. i tried casting them in wax and ensured the wax got between all the petals and intended to wash the clay out of the mould afterwards but the clay needed some scraping to remove and i damaged the wax that had gone between the petals. i was thinking alginate or latex would work better as it is stretchier and less brittle/fragile but alginate would still be very breakable in the spaces between petals as well as a little too floppy and if i used latex i wouldnt be able to then fill the mould with latex to make the flowers. is there another casting material i am not thinking of or is there a way of casting something in latex in a latex mould without it sticking?