What is a good way to make a model black hole? Im doing mine for school, and i made it i plasticine and the materials to make a cast, was there a better way? ( i need to roll marbles on it )

make it like a cone shape so the marbles would roll into it. if you wanted something like the picture you could make it out of cardboard and paint it and put a stand under it :D i love paint. it doesnt taste good though.