Sifting for fossils requires…… a sifter! Below are links to some easy instructions for building the ideal tool. That said, anything that separates bigger pieces from sand is a good stand-in – like a kitchen strainer or a sieve from the sand box. “We” made our sifter from scrap wood, left over screen and roof tacks. If you have a deep-set old picture frame, you could just staple some screen to that. Or a quick search online will give you lots of options for buying one.
Or here are easy-to-follow instructions for the traditional wooden kind: