Gauge as written was a little too loose for my taste with this particular yarn. Working as follows after first attempt wasn’t quite what I needed.

Long Tail Cast On 42 sts.
Using US 1 1/2 - 2.25mm needles for entire project.
K1 through back loop, p1 for 24 rounds.
Knit 8 rows stockinette.
Begin thumb gusset.
Knit 2 3/4” before working decreases.
Knit 11 rows of thumb.
Work K2tog on rows 12 & 14.
7 sts left to weave tail through.