CO 50 stitches and arrange them on the double-pointed needles.  

Join into a round, place a ring marker between first and last stitch.

Rounds 1:  Knit.

Round 2: Purl.

Round 3: Knit. 

Round 4:  *K3, k2tog, yo, repeat from * to end of round. 

Round 5:  Knit.

Round 6 (Decrease Round):  *K3, k2tog, repeat from * to end of round. 40 stitches remaining.

Rounds 7 and 8:  Knit.

Round 9 (Decrease Round):  *K2, k2tog, repeat from * to end of round. 30 stitches remaining.

Rounds 10 and 11: Knit.

Round 12 (Decrease Round):  *K1, k2tog, repeat from * to end of round. 20 stitches remaining.

Round 13:  Knit.  

Round 14 (Decrease Round):  *K2tog, repeat from * to end of round. 10 stitches remaining. 

Repeat Round 14.  5 stitches remaining.

Bind off remaining 5 stitches and weave in ends. Make as many coaster tops as you like, then block them lightly to flatten them.