Use a sharp knife to cut the watermelon into thick chunks, approximately 2-inch pieces, ensuring each piece can hold a popsicle stick.
Insert a popsicle stick into the center of each watermelon chunk, pressing firmly to ensure it stays in place during freezing.
Arrange the watermelon chunks with sticks upright in watermelon popsicle molds, filling each mold to the top.
Place the molds with the watermelon chunks in the freezer and freeze for at least 4 hours, or until completely solid.
Once frozen, remove the molds from the freezer and run warm water briefly over the outside of each mold to loosen the popsicles.
Carefully pull out the watermelon popsicles from the molds, holding the sticks, and serve immediately or store in a sealed container in the freezer.