This video shows how to knit a C3B without using a cable needle.

To work a C3B right leaning cable without a cable needle, with RS facing and working into the front of the stitches, knit the 2nd and 3rd sts on the left hand needle; then, without slipping these stitches off the needle, knit the 1st stitch on the left hand needle; with the new loops now on the right hand needle, slip the worked 2nd and 3rd stitches off the left hand needle.