Knit flat, then seamed.
Ballband recipe, but changing colours at 8 rows.

cast on 44 on 3.5mm (I did a long tail cast on for stretch)
knit 3 rows
stocking stitch for 20 cm
(I did 8 rows black, 8 rows grey, ending with black)
2 rows garter stitch, cast off knit wise

seam 4 cm from cast on edge, leave a 4 cm gap, continue seaming to cast off edge.