Open your walnut by prying it gently apart. Gut the walnut out until it is clean.
File the base (the flat part of the shell) so that when the two halves fit together there is a large space to fit a popsicle stick as the handle.
Spread Elmer’s glue all the way around the base of one shell half. Put glue on both sides of one end of the popsicle stick. Place the uncooked rice in the other half (the unglued half) of the walnut shell.
Fit the two halves together and place the popsicle stick as the handle between the two, where you filed a space for it.
Wrap the rubber band around the shell to hold the maraca in place for 24 hours while the glue dries.