Knitting from the middle of a skein?

Okay, here’s another question I have. For a keyhole scarf, I found a pattern in which the person “cast on using yarn from the middle of a skein.” I’ve never done this. Is the easiest way to do this to just roll the yarn into 2 balls (one from each end)?

For a keyhole scarf, there is a time (when you’re making the slit) that you use two strands of yarn. They’re saying to use both ends of the skein for that part of the scarf. You’ll go back to using one strand after the slit is done.