I’m currently kntting this pattern. I’m confused as to the cast on in the middle of a row. In left back, step two of the pattern, you pick up sts, then skip ridges, then cast on 30 stiches using the thumb method. Do I break the yarn after the pick up in order to cast on? I’m not sure. If I leave the yarn attached, then how do I do the thumb cast on with the end still attahced to the last stich and also to the ball of yarn? Help!