the front, then back on the needle, in that order.
once you have all the pieces on one needle, using only the ball of yarn attached to the first piece [and cutting the other ball(s)], work across the first piece, cast on the number of stitches indicated for the underarm, placing a marker in the middle of these cast-on stitches, work across the second piece and cast on the underarm stitches and place another marker in the middle of the cast-on stitches. if you’re working a completed front, the second marker will mark the beginning of the round, and you’re now ready to work in the round. if you’re working with 