For other beginners, there are two parts of the pattern I was unsure of how to proceed and here’s my understanding of what to do.

When it says to put the sleeves on a holder, it means the two 26-stitch (prior to the increases) sections denoted by the markers. I just used a bit of spare yarn as a stitch holder.

I was confused by where/how to cast on the stitches for the underarm. I talked to a more experienced knitting friend and she said to knit the last w.s. row as usual and NOT take the sleeve stitches off, but to do this instead in the same row as the increases and cast-ons.

On the row with that instruction, once you do the increase, K1, remove the marker, then slip the stitches onto scrap yarn, and do a single needle cast on of 4 stitches (onto the right needle), then you continue as per the pattern (repeating this for the other sleeve).

For the last buttonhole, which should appear in the bottom garter stitch border, the 10th ridge should be knit the entire way on the wrong side to begin the border. Then you do the buttonhole row, 2 more knit rows, then cast off. I skipped the bottom decorative rows, but if want to put them in, you’d have to count backwards to figure out where they go since the pattern doesn’t specify.

Washing instructions:
100% cotton
Machine wash warm (40°C), gentle cycle
Iron medium heat (two dots)
Dry clean (A - any solvent)
Do not bleach, do not tumble dry.
Dry flat, in shade.