Being all thumbs…
There must be a dozen ways to do a mitten thumb, with a dozen degrees of difficulty.
Some thumbs need to have designated lefts and rights (like these), others just poke off the side so you can switch them up on either hand. Some grow from making stitches, others from picking up live stitches parked on waste yarn. Knitters have their favorites, based on technique, comfort, style, etc.
Simply put, thumbs take thought. And thumbs done in “left” and “right” versions simultaneously on one circular require concentration. Deep concentration. This is not knitting you attempt anywhere but in peaceful silence with a calming beverage at your side.
Making the crochet chains was not difficult. Installing them in halves proved a bit more complex. I used the old trick of different color stitch markers to ensure I knew where I was at all times. There were points where it looked as if I was merely holding a tangle of needles, cords, yarn, and knots. I’m certain lots of squinting and frowning was involved. Thumbs are often one of those techniques—like entrelac—where I find myself staring at the knitting and going “Huh? Is this right?”
But then, the desired form begins to emerge, the perfect little pocket for your opposable digit comes to life, and you can only smile.
And give, of course, a “thumbs up.”