1st row - K1, cast off 5 sts (thumbhole), knit to end.
2nd row - Purl to last st, turn, cast on 5 sts, turn, P1
After you bind off 5 sts and knit to the end, turn your work and purl to the last st. before the bind off. Turn the right needle and cast on 5 sts, turn it back to normal position and purl the last st, which was the K1 from row 1.
This is the last time I'm frogging this project for the last time.