At the end of the first row of the heel turning, you will have some stitches unworked still on the left-hand needle. Don't worry about them; they'll be fine.
Instead, turn the work as you would in regular flat knitting when you reached the end of the row. That means the needle with those unworked stitches should now be in your right hand and the needle with the stitches you did work on the last row will be in your left hand.
Knit back across these stitches as the pattern indicates. In the case of our example you'd slip the first stitch, knit 4, slip, slip, knit, knit one more and turn the work again. Now you have unworked stitches on both needles and just a few stitches that have been worked on both rows.