Tubular Cast-on is a technique which creates a neat edge with elasticity. It is particularly suited when continuing with k1/p1 ribbing.
Using the provisional crochet cast-on method, and needles 1 or 2 sizes larger than the needles you will work with with, cast on half the number of stitches desired upon completion of the tubular cast-on. In this tutorial, we will provisionally cast on 8 sts.
Turn work. Starting with a purl row (and larger needles), work three rows in stocking stitch.
Now, remove the provisional cast on (unzip), placing the live stitches onto another circular needle.
In this tutorial, the metal needles are the larger needles. The wooden needles are the smaller needles on which the stitches recovered from the provisional cast on have been placed.
This is the situation just after the stitches have been removed from the provisional cast on: the metal needle is pointing to the left, with the working yarn attached at the bottom left of the picture. The wooden needle is pointing to the right, where the last stitch has been removed from the provisional cast on.
Turn your work so that the metal needle is at the top (right side of stockinette still facing). And slide the wooden circular needle to the other side so that both tips are now pointing to the right:
Bring the working/metal needle closer to you, and the wooden/spare needle to the back (WS of the stocking stitch showing), and fold in half so the wooden/spare needle is now behind the working/metal needle.
Tip: you may use a small needle / darning needle / toothpick to hold the fabric down while you fold it. Pinch the fabric and hold the two needles together, and remove whatever tool you may have used to fold your fabric
Purl one stitch from the back / spare needle…
Then knit one stitch from the front / working needle…
… and continue in this manner, alternating purling 1 st from the back, knitting 1 st from the front…