Used this pattern as inspiration. Made quite some mods (ie experimented quite a bit) due to different yarn weight mostly. Pattern itself is fine! Too bad it’s not for different yarns :)

Here’s what I did. I used DK weight yarn, and was aiming for size 0-3 months, 56-62 in Dutch sizing. Came out fine tho a bit on the smaller side, more 56.

co 52 st using longtailco
row 1 knit
row 2 k1, p1
row 3 k2, yo, k2tog, knit. 1 buttonhole created
row 4 k1, p1
row 5 knit
row 6 k1, p1
row 7 knit and incr. 4 st evenly (56)
place markers, 4 st buttonband (work in pattern), pm, 7 st shoulder, pm, 19 st back, pm, 7 st shoulder, pm, 15 st front, pm, 4 st buttonband.
row 8-10 knit in stockinette
row 11, change color, knit
row 12 purl
row 13 change color, knit
row 14 purl
row 15 k2, yo, k2tog, knit. 1 buttonhole
row 16 purl
row 17 change color, knit
row 18 purl
row 19 change color
row 20-22 knit in stockinette
row 23 change color, knit
row 24 purl
row 25 k2, yo, k2tog, knit.
row 26 purl
row 27 knit
row 28 purl
row 29 change color, knit
row 30 purl
row 31 place 4 buttonband stitches w/o buttonholes on a separate needle, hold them right behind first 4 stitches and knit together. Now continue knitting in the round.

Change color every 4 rows. I sticked to 4 rows for main color en 2 rows for cc. Work until desired length and finish with same pattern as neckline.

(notes for myself mainly, for future reference. :) )
Very pleased with result, though my boy was bigger than anticipated ;) Now working on a bigger version.