Use red yarn, start with a magic ring
R1: 7 sc in the ring, 1 ss, 1 ch
R2: ( 2 sc in next st) * 7 times, 1 ss, 1 ch
R3: (1 sc, 2 sc in next st ) * 7 times, 1 ss, 1 ch
R4: (1 sc, 2 sc in next st, 1 sc ) * 7 times, 1 ss, 1 ch
R5: (3 sc, 2 sc in next st ) * 7 times
R6: change white yarn, (2 sc, 2 sc in next st, 2 sc ) * 7 times
Then sew the watermelon seeds with black yarn.
R7: change green yarn, then fold the piece in half into a semicircle, and make 21 sc along the curved edge to bring the two sides together. 1 ch