Long Tail Cast On 54 stitches on size 9 needles
rib stitch for 4”
switch to size 11 needles
knit until 20” long
Knit buttoned bottom version

Update: My daughter slept very soundly in this sleep sack and I felt safe with her in it. If I made another one I would maybe not make the button opening at the bottom. The only times that came in handy was to wiggle my hands inside the sack to make sure her feet weren’t cold. Otherwise, the round bottom would be better as it doesn’t have a seam that seems to annoy my daughter if it’s not on her straight.

I also love this yarn for the sleep sacks. While it starts to pill after a few washings, the fabric it makes is both breathable and warm so my baby is comfortable but not overly hot.