Instead of k2tog which will decrease one stitch, this will end with 2 sts on the right hand needle. So k2tog as usual but don't slip the stitches off the left hand needle. Bring the right hand needle around and knit into the first stitch again. Now you have 2 loops over the right hand needle and you can slip the original 2 stitches off the left hand needle.
It may help to try this a few times with some scrap yarn just for practice,