Blow up the balloon then let it deflate. This stretches the balloon which makes it easier to fill.
STEP 2: Insert the funnel
Pull the end of the balloon up over the end of a funnel.
STEP 3: Pour in the rice
Carefully pour the rice into the funnel. Shake the funnel back and forth, tapping the side to get the rice to go down into the balloon.
Keep adding rice to the funnel and into the balloon until you're happy with the size of your stress ball. To make more space inside, pinch the neck of the balloon closed and press your fingers down right below the funnel, pushing the rice down and outwards.
STEP 4: Tie a knot
Remove the funnel and tie a knot in the balloon. Try to get the knot as close to the base of the balloon as you can.
Your rice stress ball is complete!
TIP #1:
If you want to hide the knot in your stress ball, cut the neck off of a second balloon and stretch it over top. This is completely optional. It will hide the knot and make the stress ball stronger, but also less squishy.