Weaving (kitechener?) but no live stichtes?

The finishing for the sweater I want to make for my son, says

Finishing: Sew both underarm seams by weaving
Weaving should mean using Kitchener stitch, right? But I won’t have any live stitches on the arms at that point, so do I pick up stitches, on 2 needles (one needle per side) and THEN weave? Anything I’m missing?

TIA

I have seen mattress stitch referred to as weaving.

I usually just whip-stitch the underarms hole closed. It never shows.

I usually just whip-stitch the underarms hole closed. It never shows.
True, it won’t show - thanks, whip-stitch I can handle! :smiley: