Casting on in the middle of a row

I am making a poncho that is worked as a square and I am ready to complete the backside of the neck. I have a right and left hand side and my directions tell me the following:

knit 22 stitches (right side of block)
Cast on 19 stitches
knit 22 stiches (left side of block)

for a total of 63 stitches

Any direction in casting on the 19 stitches?

Thanks in advance!

When I come upon a situation like this, I just knit on the new stitches. Anything except the backward loop or long-tail methods would work, I’d guess. (No long tail available to use at that point, and backward loop would be too loose and messy).