Using medium weight, 100% cotton yarn and a size ‘H’ hook:
Chain 16
Row 1: sc in 2nd ch from hook and in ea ch to end, ch 1, turn (15 sts)
Row 2: sc in ea st across, ch 1, turn (15 sts)
Row 3: dec in 1st 2 sts, sc in next 11 sts, dec in last 2 sts, ch 1, turn (13 sts)
Row 4: sc in ea st across, ch 1, turn (13 sts)
Row 5: dec in 1st 2 sts, sc in next 9 sts, dec in last 2 sts, ch 1, turn (11 sts)
Row 6: sc in ea st across, ch 1, turn (11 sts)
Row 7: dec in 1st 2 sts, sc in next 7 sts, dec in last 2 sts, ch 1, turn (9 sts)
Row 8: sc in ea st across, ch 1, turn (9 sts)
Row 9: dec in 1st 2 sts, sc in next 5 sts, dec in last 2 sts, ch 1, turn (7 sts)
Row 10: sc in ea st across, ch 1, turn (7 sts)
Row 11: dec in 1st 2 sts, sc in next 3 sts, dec in last 2 sts, ch 1, turn (5 sts)
Row 12: sc in ea st across, ch 1, turn (5 sts)
Row 13: dec in 1st 2 sts, sc in next st, dec in last 2 sts, ch 1, turn (3 sts)
Row 14: sc in ea st across, ch 1, turn (3 sts)
Row 15: sc3tog, ch 1, do not turn (1 st)
Edge: sc in ea row end and st around coaster, making 4 sc in ea lower corner and 3 sc in top point; join to first sc of edge; fasten off and weave in ends.

Finish coasters by weaving a narrow grosgrain ribbon inside the edge and fasten a star button to the top. I just used the end of the ribbon to secure the button before I wove the ribbon end in.