If you wish use invisible stitches to sew the upper front and back under the buttons.

Garment measurements:
Bust 90/98/106/114 cm (35½”/38½”/41¾”/45”)
Length approx. 51/52/53/55 cm (20”/20½”/20¾”/21¾”)

Materials:
LANGYARNS ALPACA SUPERLIGHT (alpaca superfine, nylon, fine merino) 75/75/100/125 g - 3/3/4/5 balls of light blue 749.0033.
ADDI knitting needles, size 4mm (US 6, UK 8).
12 small buttons.