It helps when your number is easily divisible by 2 other ones, and 115 isn't. You could do a round that decreases 7sts evenly spaced to get you down to 108 sts. Then do the crown decs as k10, k2tog 9 times around, and one plain round. On the next one it would be k9, k2tog, 9 times around and a plain round after that. Keep that up, knitting 1 less stitch between the decs every other round until you're down to about 4 sts between the k2togs, then dec every round. When you're at about 18 sts, you could cut the tail and pull it through the last of the stitches, or if that's too many, then k1 k2tog one more round so you have 12 stitches and finish it off.
eta - I got to thinking you might need fewer decrease rounds so it wouldn't be too long, so you could do an initial decrease of 5 sts to 110 sts, then start with either k8, k2tog 11 times, or k9, k2tog 10 times. Then still do a plain round between the dec rounds and 1 less stitch between decs.